diff --git a/accessible/base/SelectionManager.cpp b/accessible/base/SelectionManager.cpp
index 1c3788036a08..d846e356bc87 100644
--- a/accessible/base/SelectionManager.cpp
+++ b/accessible/base/SelectionManager.cpp
@@ -12,6 +12,7 @@
 #include "nsAccUtils.h"
 #include "nsCoreUtils.h"
 #include "nsEventShell.h"
+#include "nsFrameSelection.h"
 
 #include "nsIAccessibleTypes.h"
 #include "nsIDOMDocument.h"
diff --git a/accessible/generic/HyperTextAccessible-inl.h b/accessible/generic/HyperTextAccessible-inl.h
index f47a0e200941..81e421536839 100644
--- a/accessible/generic/HyperTextAccessible-inl.h
+++ b/accessible/generic/HyperTextAccessible-inl.h
@@ -14,6 +14,7 @@
 #include "nsIEditor.h"
 #include "nsIPersistentProperties2.h"
 #include "nsIPlaintextEditor.h"
+#include "nsFrameSelection.h"
 
 namespace mozilla {
 namespace a11y {
@@ -143,7 +144,7 @@ HyperTextAccessible::IsCaretAtEndOfLine() const
 {
   nsRefPtr<nsFrameSelection> frameSelection = FrameSelection();
   return frameSelection &&
-    frameSelection->GetHint() == nsFrameSelection::HINTLEFT;
+    frameSelection->GetHint() == CARET_ASSOCIATE_BEFORE;
 }
 
 inline already_AddRefed<nsFrameSelection>
diff --git a/accessible/generic/HyperTextAccessible.cpp b/accessible/generic/HyperTextAccessible.cpp
index 738d3b00f0fa..cac3b749eb1f 100644
--- a/accessible/generic/HyperTextAccessible.cpp
+++ b/accessible/generic/HyperTextAccessible.cpp
@@ -1269,7 +1269,7 @@ HyperTextAccessible::CaretLineNumber()
 
   int32_t returnOffsetUnused;
   uint32_t caretOffset = domSel->FocusOffset();
-  nsFrameSelection::HINT hint = frameSelection->GetHint();
+  CaretAssociationHint hint = frameSelection->GetHint();
   nsIFrame *caretFrame = frameSelection->GetFrameForNodeOffset(caretContent, caretOffset,
                                                                hint, &returnOffsetUnused);
   NS_ENSURE_TRUE(caretFrame, -1);
diff --git a/accessible/generic/HyperTextAccessible.h b/accessible/generic/HyperTextAccessible.h
index 7dfd652c6adf..99f4a8338320 100644
--- a/accessible/generic/HyperTextAccessible.h
+++ b/accessible/generic/HyperTextAccessible.h
@@ -9,11 +9,22 @@
 #include "AccessibleWrap.h"
 #include "nsIAccessibleTypes.h"
 #include "xpcAccessibleHyperText.h"
+#include "nsDirection.h"
+#include "WordMovementType.h"
+#include "nsIFrame.h"
 
-#include "nsFrameSelection.h"
 #include "nsISelectionController.h"
 
+class nsFrameSelection;
+class nsRange;
+class nsIWidget;
+
 namespace mozilla {
+
+namespace dom {
+class Selection;
+}
+
 namespace a11y {
 
 class TextRange;
diff --git a/accessible/windows/sdn/sdnAccessible.cpp b/accessible/windows/sdn/sdnAccessible.cpp
index ad3a5fe8dc65..046d734c3a8a 100644
--- a/accessible/windows/sdn/sdnAccessible.cpp
+++ b/accessible/windows/sdn/sdnAccessible.cpp
@@ -17,6 +17,7 @@
 #include "nsNameSpaceManager.h"
 #include "nsServiceManagerUtils.h"
 #include "nsWinUtils.h"
+#include "nsRange.h"
 
 #include "nsAutoPtr.h"
 
diff --git a/accessible/xpcom/xpcAccessibleTextRange.cpp b/accessible/xpcom/xpcAccessibleTextRange.cpp
index 51226e4f866a..8f278979c733 100644
--- a/accessible/xpcom/xpcAccessibleTextRange.cpp
+++ b/accessible/xpcom/xpcAccessibleTextRange.cpp
@@ -8,8 +8,8 @@
 
 #include "HyperTextAccessible.h"
 #include "TextRange.h"
-
- #include "nsIMutableArray.h"
+#include "nsIMutableArray.h"
+#include "nsComponentManagerUtils.h"
 
 using namespace mozilla;
 using namespace mozilla::a11y;
diff --git a/content/html/content/src/nsTextEditorState.cpp b/content/html/content/src/nsTextEditorState.cpp
index 9bb4f03f98e8..7989c94e035f 100644
--- a/content/html/content/src/nsTextEditorState.cpp
+++ b/content/html/content/src/nsTextEditorState.cpp
@@ -45,6 +45,7 @@
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/dom/HTMLInputElement.h"
 #include "nsNumberControlFrame.h"
+#include "nsFrameSelection.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -546,7 +547,7 @@ nsTextInputSelectionImpl::CompleteMove(bool aForward, bool aExtend)
 
   // make the caret be either at the very beginning (0) or the very end
   int32_t offset = 0;
-  nsFrameSelection::HINT hint = nsFrameSelection::HINTLEFT;
+  CaretAssociationHint hint = CARET_ASSOCIATE_BEFORE;
   if (aForward)
   {
     offset = parentDIV->GetChildCount();
@@ -561,7 +562,7 @@ nsTextInputSelectionImpl::CompleteMove(bool aForward, bool aExtend)
       if (child->Tag() == nsGkAtoms::br)
       {
         --offset;
-        hint = nsFrameSelection::HINTRIGHT; // for Bug 106855
+        hint = CARET_ASSOCIATE_AFTER; // for Bug 106855
       }
     }
   }
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index cea15c8e38b6..302deea54bb3 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -40,6 +40,7 @@
 #include "nsWindowMemoryReporter.h"
 #include "WindowNamedPropertiesHandler.h"
 #include "nsFrameSelection.h"
+#include "nsISelectionListener.h"
 
 // Helper Classes
 #include "nsJSUtils.h"
diff --git a/dom/events/ContentEventHandler.cpp b/dom/events/ContentEventHandler.cpp
index 5fcffd9d9d19..65f48d9a3ffe 100644
--- a/dom/events/ContentEventHandler.cpp
+++ b/dom/events/ContentEventHandler.cpp
@@ -440,8 +440,8 @@ ContentEventHandler::ExpandToClusterBoundary(nsIContent* aContent,
 
   nsRefPtr<nsFrameSelection> fs = mPresShell->FrameSelection();
   int32_t offsetInFrame;
-  nsFrameSelection::HINT hint =
-    aForward ? nsFrameSelection::HINTLEFT : nsFrameSelection::HINTRIGHT;
+  CaretAssociationHint hint =
+    aForward ? CARET_ASSOCIATE_BEFORE : CARET_ASSOCIATE_AFTER;
   nsIFrame* frame = fs->GetFrameForNodeOffset(aContent, int32_t(*aXPOffset),
                                               hint, &offsetInFrame);
   if (!frame) {
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index 98d56d562e52..a1edf28dd587 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -55,6 +55,7 @@ using mozilla::DefaultXDisplay;
 #include "mozilla/MouseEvents.h"
 #include "mozilla/TextEvents.h"
 #include "mozilla/dom/HTMLObjectElementBinding.h"
+#include "nsFrameSelection.h"
 
 #include "nsContentCID.h"
 #include "nsWidgetsCID.h"
diff --git a/editor/libeditor/html/tests/test_bug674770-1.html b/editor/libeditor/html/tests/test_bug674770-1.html
index b422d2ee1769..f202a909897a 100644
--- a/editor/libeditor/html/tests/test_bug674770-1.html
+++ b/editor/libeditor/html/tests/test_bug674770-1.html
@@ -22,11 +22,6 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=674770
 <pre id="test">
 <script type="application/javascript">
 
-if (!navigator.platform.startsWith("Linux")) {
-  SimpleTest.expectAssertions(1);
-}
-
-/** Test for Bug 674770 **/
 SimpleTest.waitForExplicitFinish();
 SimpleTest.waitForFocus(function() {
   SpecialPowers.setBoolPref("middlemouse.paste", true);
diff --git a/layout/base/CaretAssociationHint.h b/layout/base/CaretAssociationHint.h
new file mode 100644
index 000000000000..52bb5ba5b024
--- /dev/null
+++ b/layout/base/CaretAssociationHint.h
@@ -0,0 +1,22 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef CaretAssociationHint_h___
+#define CaretAssociationHint_h___
+
+namespace mozilla {
+
+/**
+ * Hint whether a caret is associated with the content before a
+ * given character offset (ASSOCIATE_BEFORE), or with the content after a given
+ * character offset (ASSOCIATE_AFTER).
+ */
+enum CaretAssociationHint {
+  CARET_ASSOCIATE_BEFORE,
+  CARET_ASSOCIATE_AFTER
+};
+
+}
+
+#endif
diff --git a/layout/base/SelectionCarets.cpp b/layout/base/SelectionCarets.cpp
index cbf7ea9e6b38..510a78262589 100644
--- a/layout/base/SelectionCarets.cpp
+++ b/layout/base/SelectionCarets.cpp
@@ -29,6 +29,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/TouchEvents.h"
 #include "TouchCaret.h"
+#include "nsFrameSelection.h"
 
 using namespace mozilla;
 
@@ -322,7 +323,7 @@ FindFirstNodeWithFrame(nsIDocument* aDocument,
 
   nsCOMPtr<nsIContent> startContent = do_QueryInterface(startNode);
   nsCOMPtr<nsIContent> endContent = do_QueryInterface(endNode);
-  nsFrameSelection::HINT hintStart =
+  CaretAssociationHint hintStart =
     nsFrameSelection::GetHintForPosition(startContent, offset);
   nsIFrame* startFrame = aFrameSelection->GetFrameForNodeOffset(startContent,
                                                                 offset,
@@ -546,20 +547,20 @@ CompareRangeWithContentOffset(nsRange* aRange,
   MOZ_ASSERT(aDragMode != SelectionCarets::NONE);
   nsINode* node = nullptr;
   int32_t nodeOffset = 0;
-  nsFrameSelection::HINT hint = nsFrameSelection::HINTLEFT;
+  CaretAssociationHint hint;
   nsDirection dir;
 
   if (aDragMode == SelectionCarets::START_FRAME) {
     // Check previous character of end node offset
     node = aRange->GetEndParent();
     nodeOffset = aRange->EndOffset();
-    hint = nsFrameSelection::HINTLEFT;
+    hint = CARET_ASSOCIATE_BEFORE;
     dir = eDirPrevious;
   } else {
     // Check next character of start node offset
     node = aRange->GetStartParent();
     nodeOffset = aRange->StartOffset();
-    hint = nsFrameSelection::HINTRIGHT;
+    hint =  CARET_ASSOCIATE_AFTER;
     dir = eDirNext;
   }
   nsCOMPtr<nsIContent> content = do_QueryInterface(node);
@@ -649,7 +650,7 @@ SelectionCarets::DragSelection(const nsPoint &movePoint)
                   offsets.EndOffset(),
                   true,
                   false,
-                  offsets.associateWithNext);
+                  offsets.associate);
   if (!weakScrollable.IsAlive()) {
     return nsEventStatus_eConsumeNoDefault;
   }
@@ -693,7 +694,7 @@ SelectionCarets::GetCaretYCenterPosition()
   }
 
   int32_t offset;
-  nsFrameSelection::HINT hint =
+  CaretAssociationHint hint =
     nsFrameSelection::GetHintForPosition(node, nodeOffset);
   nsIFrame* theFrame =
     fs->GetFrameForNodeOffset(node, nodeOffset, hint, &offset);
diff --git a/layout/base/TouchCaret.cpp b/layout/base/TouchCaret.cpp
index cbe8f68253b2..79626846e444 100644
--- a/layout/base/TouchCaret.cpp
+++ b/layout/base/TouchCaret.cpp
@@ -287,7 +287,7 @@ TouchCaret::MoveCaret(const nsPoint& movePoint)
                   offsets.EndOffset(),
                   false,
                   false,
-                  offsets.associateWithNext);
+                  offsets.associate);
 
   if (!weakScrollable.IsAlive()) {
     return;
diff --git a/layout/base/TouchCaret.h b/layout/base/TouchCaret.h
index 0474041c5a67..48a7263a615c 100644
--- a/layout/base/TouchCaret.h
+++ b/layout/base/TouchCaret.h
@@ -10,7 +10,6 @@
 #include "nsISelectionListener.h"
 #include "nsIScrollObserver.h"
 #include "nsIWeakReferenceUtils.h"
-#include "nsFrameSelection.h"
 #include "nsITimer.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/TouchEvents.h"
diff --git a/layout/base/WordMovementType.h b/layout/base/WordMovementType.h
new file mode 100644
index 000000000000..c1d64a7a651d
--- /dev/null
+++ b/layout/base/WordMovementType.h
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WordMovementType_h___
+#define WordMovementType_h___
+
+namespace mozilla {
+
+enum EWordMovementType { eStartWord, eEndWord, eDefaultBehavior };
+
+}
+
+#endif
diff --git a/layout/base/moz.build b/layout/base/moz.build
index 98af57a820c0..60ebd7ef9779 100644
--- a/layout/base/moz.build
+++ b/layout/base/moz.build
@@ -17,6 +17,7 @@ XPIDL_MODULE = 'layout_base'
 
 EXPORTS += [
     'ActiveLayerTracker.h',
+    'CaretAssociationHint.h',
     'DisplayItemClip.h',
     'DisplayListClipState.h',
     'FrameLayerBuilder.h',
@@ -52,6 +53,7 @@ EXPORTS += [
     'StackArena.h',
     'Units.h',
     'UnitTransforms.h',
+    'WordMovementType.h',
 ]
 
 EXPORTS.mozilla += [
diff --git a/layout/base/nsCaret.cpp b/layout/base/nsCaret.cpp
index 31246ad05391..05f7de59572d 100644
--- a/layout/base/nsCaret.cpp
+++ b/layout/base/nsCaret.cpp
@@ -121,7 +121,7 @@ nsCaret::nsCaret()
 , mKeyboardRTL(false)
 , mLastBidiLevel(0)
 , mLastContentOffset(0)
-, mLastHint(nsFrameSelection::HINTLEFT)
+, mLastHint(CARET_ASSOCIATE_BEFORE)
 {
 }
 
@@ -597,11 +597,11 @@ void nsCaret::StopBlinking()
 }
 
 bool
-nsCaret::DrawAtPositionWithHint(nsIDOMNode*             aNode,
-                                int32_t                 aOffset,
-                                nsFrameSelection::HINT  aFrameHint,
-                                uint8_t                 aBidiLevel,
-                                bool                    aInvalidate)
+nsCaret::DrawAtPositionWithHint(nsIDOMNode*          aNode,
+                                int32_t              aOffset,
+                                CaretAssociationHint aFrameHint,
+                                uint8_t              aBidiLevel,
+                                bool                 aInvalidate)
 {
   nsCOMPtr<nsIContent> contentNode = do_QueryInterface(aNode);
   if (!contentNode)
@@ -664,13 +664,13 @@ IsBidiUI()
 }
 
 nsresult 
-nsCaret::GetCaretFrameForNodeOffset(nsFrameSelection*      aFrameSelection,
-                                    nsIContent*            aContentNode,
-                                    int32_t                aOffset,
-                                    nsFrameSelection::HINT aFrameHint,
-                                    uint8_t                aBidiLevel,
-                                    nsIFrame**             aReturnFrame,
-                                    int32_t*               aReturnOffset)
+nsCaret::GetCaretFrameForNodeOffset(nsFrameSelection*    aFrameSelection,
+                                    nsIContent*          aContentNode,
+                                    int32_t              aOffset,
+                                    CaretAssociationHint aFrameHint,
+                                    uint8_t              aBidiLevel,
+                                    nsIFrame**           aReturnFrame,
+                                    int32_t*             aReturnOffset)
 {
   if (!aFrameSelection)
     return NS_ERROR_FAILURE;
@@ -974,7 +974,7 @@ void nsCaret::DrawCaret(bool aInvalidate)
 
   nsCOMPtr<nsIDOMNode> node;
   int32_t offset;
-  nsFrameSelection::HINT hint;
+  CaretAssociationHint hint;
   uint8_t bidiLevel;
 
   if (!mDrawn)
@@ -990,7 +990,7 @@ void nsCaret::DrawCaret(bool aInvalidate)
 
     bool hintRight;
     privateSelection->GetInterlinePosition(&hintRight);//translate hint.
-    hint = hintRight ? nsFrameSelection::HINTRIGHT : nsFrameSelection::HINTLEFT;
+    hint = hintRight ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
 
     // get the node and offset, which is where we want the caret to draw
     domSelection->GetFocusNode(getter_AddRefs(node));
diff --git a/layout/base/nsCaret.h b/layout/base/nsCaret.h
index bde04fa2bde6..0b852b4c2df3 100644
--- a/layout/base/nsCaret.h
+++ b/layout/base/nsCaret.h
@@ -13,11 +13,19 @@
 #include "nsCoord.h"
 #include "nsISelectionListener.h"
 #include "nsIWeakReferenceUtils.h"
-#include "nsFrameSelection.h"
+#include "CaretAssociationHint.h"
+#include "nsPoint.h"
+#include "nsRect.h"
 
-class nsRenderingContext;
 class nsDisplayListBuilder;
+class nsFrameSelection;
+class nsIContent;
+class nsIDOMNode;
+class nsIFrame;
+class nsINode;
+class nsIPresShell;
 class nsITimer;
+class nsRenderingContext;
 
 //-----------------------------------------------------------------------------
 class nsCaret : public nsISelectionListener
@@ -31,6 +39,8 @@ class nsCaret : public nsISelectionListener
   public:
     NS_DECL_ISUPPORTS
 
+    typedef mozilla::CaretAssociationHint CaretAssociationHint;
+
     nsresult Init(nsIPresShell *inPresShell);
     void Terminate();
 
@@ -142,7 +152,7 @@ class nsCaret : public nsISelectionListener
     static nsresult GetCaretFrameForNodeOffset(nsFrameSelection* aFrameSelection,
                                                nsIContent* aContentNode,
                                                int32_t aOffset,
-                                               nsFrameSelection::HINT aFrameHint,
+                                               CaretAssociationHint aFrameHint,
                                                uint8_t aBidiLevel,
                                                nsIFrame** aReturnFrame,
                                                int32_t* aReturnOffset);
@@ -160,7 +170,7 @@ protected:
 
     bool          DrawAtPositionWithHint(nsIDOMNode* aNode,
                                          int32_t aOffset,
-                                         nsFrameSelection::HINT aFrameHint,
+                                         CaretAssociationHint aFrameHint,
                                          uint8_t aBidiLevel,
                                          bool aInvalidate);
 
@@ -233,7 +243,7 @@ protected:
                                               // actually drawn (anon <BR> in text control)
     int32_t               mLastContentOffset; // the offset for the last request
 
-    nsFrameSelection::HINT mLastHint;        // the hint associated with the last request, see also
+    CaretAssociationHint  mLastHint;          // the hint associated with the last request, see also
                                               // mLastBidiLevel below
 
 };
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index ff650b67d2ad..ea3ab2a2d346 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -10,11 +10,13 @@
  * used during painting and hit testing
  */
 
-#include "mozilla/dom/TabChild.h"
-#include "mozilla/layers/PLayerTransaction.h"
-
 #include "nsDisplayList.h"
 
+#include <stdint.h>
+#include <algorithm>
+
+#include "mozilla/dom/TabChild.h"
+#include "mozilla/layers/PLayerTransaction.h"
 #include "nsCSSRendering.h"
 #include "nsRenderingContext.h"
 #include "nsISelectionController.h"
@@ -56,9 +58,8 @@
 #include "UnitTransforms.h"
 #include "LayersLogging.h"
 #include "FrameLayerBuilder.h"
-
-#include <stdint.h>
-#include <algorithm>
+#include "nsCaret.h"
+#include "nsISelection.h"
 
 using namespace mozilla;
 using namespace mozilla::layers;
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 197d8a17f55c..ce7330dafbe2 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -84,6 +84,8 @@
 #include "nsIContentViewer.h"
 #include "LayersLogging.h"
 #include "mozilla/Preferences.h"
+#include "nsFrameSelection.h"
+#include "FrameLayerBuilder.h"
 
 #ifdef MOZ_XUL
 #include "nsXULPopupManager.h"
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 8ec52777788f..43a626775880 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -119,6 +119,7 @@
 #include "nsSVGEffects.h"
 #include "SVGFragmentIdentifier.h"
 #include "nsArenaMemoryStats.h"
+#include "nsFrameSelection.h"
 
 #include "nsPerformance.h"
 #include "nsRefreshDriver.h"
@@ -2433,7 +2434,8 @@ PresShell::CompleteMove(bool aForward, bool aExtend)
   nsIFrame::CaretPosition pos =
     frame->GetExtremeCaretPosition(!aForward);
   mSelection->HandleClick(pos.mResultContent, pos.mContentOffset,
-                          pos.mContentOffset, aExtend, false, aForward);
+                          pos.mContentOffset, aExtend, false,
+                          aForward ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE);
   if (limiter) {
     // HandleClick resets ancestorLimiter, so set it again.
     mSelection->SetAncestorLimiter(limiter);
@@ -2656,6 +2658,19 @@ PresShell::RestoreRootScrollPosition()
   }
 }
 
+void
+PresShell::MaybeReleaseCapturingContent()
+{
+  nsRefPtr<nsFrameSelection> frameSelection = FrameSelection();
+  if (frameSelection) {
+    frameSelection->SetDragState(false);
+  }
+  if (gCaptureInfo.mContent &&
+      gCaptureInfo.mContent->OwnerDoc() == mDocument) {
+    SetCapturingContent(nullptr, 0);
+  }
+}
+
 void
 PresShell::BeginLoad(nsIDocument *aDocument)
 {
diff --git a/layout/base/nsPresShell.h b/layout/base/nsPresShell.h
index d73339bd4def..2809ff5e00e3 100644
--- a/layout/base/nsPresShell.h
+++ b/layout/base/nsPresShell.h
@@ -30,7 +30,6 @@
 #include "nsAutoPtr.h"
 #include "nsIWidget.h"
 #include "nsStyleSet.h"
-#include "nsFrameSelection.h"
 #include "nsContentUtils.h" // For AddScriptBlocker().
 #include "nsRefreshDriver.h"
 #include "mozilla/Attributes.h"
@@ -546,17 +545,7 @@ protected:
   // Utility method to restore the root scrollframe state
   void RestoreRootScrollPosition();
 
-  void MaybeReleaseCapturingContent()
-  {
-    nsRefPtr<nsFrameSelection> frameSelection = FrameSelection();
-    if (frameSelection) {
-      frameSelection->SetDragState(false);
-    }
-    if (gCaptureInfo.mContent &&
-        gCaptureInfo.mContent->OwnerDoc() == mDocument) {
-      SetCapturingContent(nullptr, 0);
-    }
-  }
+  void MaybeReleaseCapturingContent();
 
   nsresult HandleRetargetedEvent(mozilla::WidgetEvent* aEvent,
                                  nsEventStatus* aStatus,
diff --git a/layout/forms/nsImageControlFrame.cpp b/layout/forms/nsImageControlFrame.cpp
index 57c1ac44a94d..e7070a8d2125 100644
--- a/layout/forms/nsImageControlFrame.cpp
+++ b/layout/forms/nsImageControlFrame.cpp
@@ -2,6 +2,7 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 #include "nsImageFrame.h"
 #include "nsIFormControlFrame.h"
 #include "nsPresContext.h"
@@ -10,6 +11,7 @@
 #include "nsFormControlFrame.h"
 #include "nsLayoutUtils.h"
 #include "mozilla/MouseEvents.h"
+#include "nsIContent.h"
 
 using namespace mozilla;
 
diff --git a/layout/generic/TextOverflow.cpp b/layout/generic/TextOverflow.cpp
index 29d514f4aa69..b4d20336625b 100644
--- a/layout/generic/TextOverflow.cpp
+++ b/layout/generic/TextOverflow.cpp
@@ -22,6 +22,7 @@
 #include "nsIFrameInlines.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Likely.h"
+#include "nsISelection.h"
 
 namespace mozilla {
 namespace css {
diff --git a/layout/generic/nsBRFrame.cpp b/layout/generic/nsBRFrame.cpp
index 61b8792ca3da..d314e98cb32d 100644
--- a/layout/generic/nsBRFrame.cpp
+++ b/layout/generic/nsBRFrame.cpp
@@ -208,7 +208,7 @@ nsIFrame::ContentOffsets BRFrame::CalcContentOffsetsFromFramePoint(nsPoint aPoin
   if (offsets.content) {
     offsets.offset = offsets.content->IndexOf(mContent);
     offsets.secondaryOffset = offsets.offset;
-    offsets.associateWithNext = true;
+    offsets.associate = CARET_ASSOCIATE_AFTER;
   }
   return offsets;
 }
diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index ee054de8f396..e115517b9618 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -49,6 +49,7 @@
 #include "TextOverflow.h"
 #include "nsIFrameInlines.h"
 #include "CounterStyleManager.h"
+#include "nsISelection.h"
 
 #include "nsBidiPresUtils.h"
 
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index 65c5c73f4ec1..cc58c5184a70 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -2817,7 +2817,7 @@ nsFrame::HandlePress(nsPresContext* aPresContext,
 
     return fc->HandleClick(offsets.content, offsets.StartOffset(),
                            offsets.EndOffset(), false, false,
-                           offsets.associateWithNext);
+                           offsets.associate);
   }
 
   // Let Ctrl/Cmd+mouse down do table selection instead of drag initiation
@@ -2890,7 +2890,7 @@ nsFrame::HandlePress(nsPresContext* aPresContext,
   // weakFrame checks.
   rv = fc->HandleClick(offsets.content, offsets.StartOffset(),
                        offsets.EndOffset(), mouseEvent->IsShift(), control,
-                       offsets.associateWithNext);
+                       offsets.associate);
 
   if (NS_FAILED(rv))
     return rv;
@@ -2948,8 +2948,7 @@ nsFrame::SelectByTypeAtPoint(nsPresContext* aPresContext,
     PresContext()->GetPresShell()->ConstFrameSelection();
   nsIFrame* theFrame = frameSelection->
     GetFrameForNodeOffset(offsets.content, offsets.offset,
-                          nsFrameSelection::HINT(offsets.associateWithNext),
-                          &offset);
+                          offsets.associate, &offset);
   if (!theFrame)
     return NS_ERROR_FAILURE;
 
@@ -3071,14 +3070,14 @@ nsFrame::PeekBackwardAndForward(nsSelectionAmount aAmountBack,
   rv = frameSelection->HandleClick(startpos.mResultContent,
                                    startpos.mContentOffset, startpos.mContentOffset,
                                    false, (aSelectFlags & SELECT_ACCUMULATE),
-                                   nsFrameSelection::HINTRIGHT);
+                                   CARET_ASSOCIATE_AFTER);
   if (NS_FAILED(rv))
     return rv;
 
   rv = frameSelection->HandleClick(endpos.mResultContent,
                                    endpos.mContentOffset, endpos.mContentOffset,
                                    true, false,
-                                   nsFrameSelection::HINTLEFT);
+                                   CARET_ASSOCIATE_BEFORE);
   if (NS_FAILED(rv))
     return rv;
 
@@ -3198,7 +3197,7 @@ HandleFrameSelection(nsFrameSelection*         aFrameSelection,
                                         aOffsets.EndOffset(),
                                         aFrameSelection->IsShiftDownInDelayedCaretData(),
                                         false,
-                                        aOffsets.associateWithNext);
+                                        aOffsets.associate);
       if (NS_FAILED(rv)) {
         return rv;
       }
@@ -3633,7 +3632,7 @@ nsIFrame::ContentOffsets OffsetsForSingleFrame(nsIFrame* aFrame, nsPoint aPoint)
   if (aFrame->GetNextContinuation() || aFrame->GetPrevContinuation()) {
     offsets.offset = range.start;
     offsets.secondaryOffset = range.end;
-    offsets.associateWithNext = true;
+    offsets.associate = CARET_ASSOCIATE_AFTER;
     return offsets;
   }
 
@@ -3657,7 +3656,8 @@ nsIFrame::ContentOffsets OffsetsForSingleFrame(nsIFrame* aFrame, nsPoint aPoint)
     else
       offsets.secondaryOffset = range.start;
   }
-  offsets.associateWithNext = (offsets.offset == range.start);
+  offsets.associate =
+      offsets.offset == range.start ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
   return offsets;
 }
 
@@ -3717,7 +3717,7 @@ nsIFrame::ContentOffsets nsIFrame::GetContentOffsetsFromPoint(nsPoint aPoint,
     offsets.content = closest.frame->GetContent();
     offsets.offset = 0;
     offsets.secondaryOffset = 0;
-    offsets.associateWithNext = true;
+    offsets.associate = CARET_ASSOCIATE_AFTER;
     return offsets;
   }
 
@@ -3732,7 +3732,8 @@ nsIFrame::ContentOffsets nsIFrame::GetContentOffsetsFromPoint(nsPoint aPoint,
     else
       offsets.offset = range.start;
     offsets.secondaryOffset = offsets.offset;
-    offsets.associateWithNext = (offsets.offset == range.start);
+    offsets.associate = offsets.offset == range.start ?
+        CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
     return offsets;
   }
 
@@ -5892,7 +5893,8 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
 
   aPos->mResultFrame = nullptr;
   aPos->mResultContent = nullptr;
-  aPos->mAttachForward = (aPos->mDirection == eDirNext);
+  aPos->mAttach =
+      aPos->mDirection == eDirNext ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
 
   nsAutoLineIterator it = aBlockFrame->GetLineIterator();
   if (!it)
@@ -6024,11 +6026,11 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
                 {
                   aPos->mResultContent = parent;
                   aPos->mContentOffset = parent->IndexOf(content);
-                  aPos->mAttachForward = false;
+                  aPos->mAttach = CARET_ASSOCIATE_BEFORE;
                   if ((point.x - offset.x+ tempRect.x)>tempRect.width)
                   {
                     aPos->mContentOffset++;//go to end of this frame
-                    aPos->mAttachForward = true;
+                    aPos->mAttach = CARET_ASSOCIATE_AFTER;
                   }
                   //result frame is the result frames parent.
                   aPos->mResultFrame = resultFrame->GetParent();
@@ -6048,7 +6050,7 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
               resultFrame->GetContentOffsetsFromPoint(point - offset);
           aPos->mResultContent = offsets.content;
           aPos->mContentOffset = offsets.offset;
-          aPos->mAttachForward = offsets.associateWithNext;
+          aPos->mAttach = offsets.associate;
           if (offsets.content)
           {
             bool selectable;
@@ -6092,7 +6094,7 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
             resultFrame->GetContentOffsetsFromPoint(point - offset);
         aPos->mResultContent = offsets.content;
         aPos->mContentOffset = offsets.offset;
-        aPos->mAttachForward = offsets.associateWithNext;
+        aPos->mAttach = offsets.associate;
         if (offsets.content)
         {
           bool selectable;
@@ -6101,9 +6103,9 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
           {
             found = true;
             if (resultFrame == farStoppingFrame)
-              aPos->mAttachForward = false;
+              aPos->mAttach = CARET_ASSOCIATE_BEFORE;
             else
-              aPos->mAttachForward = true;
+              aPos->mAttach = CARET_ASSOCIATE_AFTER;
             break;
           }
         }
@@ -6124,7 +6126,8 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
         //we need to jump to new block frame.
       aPos->mAmount = eSelectLine;
       aPos->mStartOffset = 0;
-      aPos->mAttachForward = !(aPos->mDirection == eDirNext);
+      aPos->mAttach = aPos->mDirection == eDirNext ?
+          CARET_ASSOCIATE_BEFORE : CARET_ASSOCIATE_AFTER;
       if (aPos->mDirection == eDirPrevious)
         aPos->mStartOffset = -1;//start from end
      return aBlockFrame->PeekOffset(aPos);
@@ -6607,7 +6610,8 @@ nsIFrame::PeekOffset(nsPeekOffsetStruct* aPos)
         --aPos->mContentOffset;
       }
       aPos->mResultFrame = targetFrame.frame;
-      aPos->mAttachForward = (aPos->mContentOffset == range.start);
+      aPos->mAttach = aPos->mContentOffset == range.start ?
+          CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
       if (!range.content)
         return NS_ERROR_FAILURE;
       return NS_OK;
@@ -8594,7 +8598,7 @@ nsIFrame::ContentOffsets::ContentOffsets(const ContentOffsets& rhs)
   : content(rhs.content),
     offset(rhs.offset),
     secondaryOffset(rhs.secondaryOffset),
-    associateWithNext(rhs.associateWithNext)
+    associate(rhs.associate)
 {
 }
 
diff --git a/layout/generic/nsFrameSelection.h b/layout/generic/nsFrameSelection.h
index 6f88cfa91a14..1822dc7dd8f4 100644
--- a/layout/generic/nsFrameSelection.h
+++ b/layout/generic/nsFrameSelection.h
@@ -14,8 +14,10 @@
 #include "nsISelectionController.h"
 #include "nsITableCellLayout.h"
 #include "nsIDOMElement.h"
-#include "nsRange.h"
+#include "WordMovementType.h"
+#include "CaretAssociationHint.h"
 
+class nsRange;
 class nsTableOuterFrame;
 
 // IID for the nsFrameSelection interface
@@ -50,8 +52,6 @@ struct SelectionDetails
 class nsIPresShell;
 class nsIScrollableFrame;
 
-enum EWordMovementType { eStartWord, eEndWord, eDefaultBehavior };
-
 /** PeekOffsetStruct is used to group various arguments (both input and output)
  *  that are passed to nsFrame::PeekOffset(). See below for the description of
  *  individual arguments.
@@ -66,22 +66,7 @@ struct MOZ_STACK_CLASS nsPeekOffsetStruct
                      bool aScrollViewStop,
                      bool aIsKeyboardSelect,
                      bool aVisual,
-                     EWordMovementType aWordMovementType = eDefaultBehavior)
-    : mAmount(aAmount)
-    , mDirection(aDirection)
-    , mStartOffset(aStartOffset)
-    , mDesiredX(aDesiredX)
-    , mWordMovementType(aWordMovementType)
-    , mJumpLines(aJumpLines)
-    , mScrollViewStop(aScrollViewStop)
-    , mIsKeyboardSelect(aIsKeyboardSelect)
-    , mVisual(aVisual)
-    , mResultContent()
-    , mResultFrame(nullptr)
-    , mContentOffset(0)
-    , mAttachForward(false)
-  {
-  }
+                     mozilla::EWordMovementType aWordMovementType = mozilla::eDefaultBehavior);
 
   // Note: Most arguments (input and output) are only used with certain values
   // of mAmount. These values are indicated for each argument below.
@@ -117,7 +102,7 @@ struct MOZ_STACK_CLASS nsPeekOffsetStruct
   //                    or to use the default beahvior, which is a combination of 
   //                    direction and the platform-based pref
   //                    "layout.word_select.eat_space_to_next_word"
-  EWordMovementType mWordMovementType;
+  mozilla::EWordMovementType mWordMovementType;
 
   // mJumpLines: Whether to allow jumping across line boundaries.
   //             Used with: eSelectCharacter, eSelectWord.
@@ -152,7 +137,7 @@ struct MOZ_STACK_CLASS nsPeekOffsetStruct
   //                 false means "the end of the frame logically before the caret", 
   //                 true means "the beginning of the frame logically after the caret".
   //                 Used with: eSelectLine, eSelectBeginLine, eSelectEndLine.
-  bool mAttachForward;
+  mozilla::CaretAssociationHint mAttach;
 };
 
 struct nsPrevNextBidiLevels
@@ -188,7 +173,8 @@ class nsIScrollableFrame;
 
 class nsFrameSelection MOZ_FINAL {
 public:
-  enum HINT { HINTLEFT = 0, HINTRIGHT = 1};  //end of this line or beginning of next
+  typedef mozilla::CaretAssociationHint CaretAssociateHint;
+
   /*interfaces for addref and release and queryinterface*/
   
   NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(nsFrameSelection)
@@ -220,7 +206,7 @@ public:
                        uint32_t aContentEndOffset,
                        bool aContinueSelection,
                        bool aMultipleSelection,
-                       bool aHint);
+                       CaretAssociateHint aHint);
 
   /** HandleDrag extends the selection to contain the frame closest to aPoint.
    *  @param aPresContext is the context to use when figuring out what frame contains the point.
@@ -387,10 +373,10 @@ public:
    * @param aOffset offset into above node.
    * @param aReturnOffset will contain offset into frame.
    */
-  virtual nsIFrame* GetFrameForNodeOffset(nsIContent *aNode,
-                                          int32_t     aOffset,
-                                          HINT        aHint,
-                                          int32_t    *aReturnOffset) const;
+  virtual nsIFrame* GetFrameForNodeOffset(nsIContent*        aNode,
+                                          int32_t            aOffset,
+                                          CaretAssociateHint aHint,
+                                          int32_t*           aReturnOffset) const;
 
   /**
    * Scrolling then moving caret placement code in common to text areas and 
@@ -409,8 +395,8 @@ public:
                       bool aExtend,
                       nsIScrollableFrame* aScrollableFrame);
 
-  void SetHint(HINT aHintRight) { mHint = aHintRight; }
-  HINT GetHint() const { return mHint; }
+  void SetHint(CaretAssociateHint aHintRight) { mHint = aHintRight; }
+  CaretAssociateHint GetHint() const { return mHint; }
 
   /** SetCaretBidiLevel sets the caret bidi level
    *  @param aLevel the caret bidi level
@@ -597,15 +583,15 @@ public:
   void DisconnectFromPresShell();
   nsresult ClearNormalSelection();
 
-  static HINT GetHintForPosition(nsIContent* aContent, int32_t aOffset);
+  static CaretAssociateHint GetHintForPosition(nsIContent* aContent, int32_t aOffset);
 
 private:
-  ~nsFrameSelection() {}
+  ~nsFrameSelection();
 
   nsresult TakeFocus(nsIContent *aNewFocus,
                      uint32_t aContentOffset,
                      uint32_t aContentEndOffset,
-                     HINT aHint,
+                     CaretAssociateHint aHint,
                      bool aContinueSelection,
                      bool aMultipleSelection);
 
@@ -613,11 +599,11 @@ private:
                          nsIContent *aNode,
                          uint32_t aContentOffset,
                          uint32_t aKeycode,
-                         HINT aHint);
+                         CaretAssociateHint aHint);
   void BidiLevelFromClick(nsIContent *aNewFocus, uint32_t aContentOffset);
   nsPrevNextBidiLevels GetPrevNextBidiLevels(nsIContent *aNode,
                                              uint32_t aContentOffset,
-                                             HINT aHint,
+                                             CaretAssociateHint aHint,
                                              bool aJumpLines) const;
 
   bool AdjustForMaintainedSelection(nsIContent *aContent, int32_t aOffset);
@@ -710,7 +696,7 @@ private:
   int16_t mSelectionChangeReason; // reason for notifications of selection changing
   int16_t mDisplaySelection; //for visual display purposes.
 
-  HINT  mHint;   //hint to tell if the selection is at the end of this line or beginning of next
+  CaretAssociateHint mHint;   //hint to tell if the selection is at the end of this line or beginning of next
   uint8_t mCaretBidiLevel;
 
   int32_t mDesiredX;
diff --git a/layout/generic/nsIFrame.h b/layout/generic/nsIFrame.h
index f709494b02f3..451a5bf83333 100644
--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -36,6 +36,7 @@
 #include "gfx3DMatrix.h"
 #include "nsLayoutUtils.h"
 #include "nsFrameState.h"
+#include "CaretAssociationHint.h"
 
 #ifdef ACCESSIBILITY
 #include "mozilla/a11y/AccTypes.h"
@@ -1256,10 +1257,10 @@ public:
     // numerical order, as opposed to wanting the primary and secondary offsets
     int32_t StartOffset() { return std::min(offset, secondaryOffset); }
     int32_t EndOffset() { return std::max(offset, secondaryOffset); }
-    // This boolean indicates whether the associated content is before or after
+    // This value indicates whether the associated content is before or after
     // the offset; the most visible use is to allow the caret to know which line
     // to display on.
-    bool associateWithNext;
+    mozilla::CaretAssociationHint associate;
   };
   enum {
     IGNORE_SELECTION_STYLE = 0x01,
diff --git a/layout/generic/nsSelection.cpp b/layout/generic/nsSelection.cpp
index e91289e41956..ef02eb1c9bbc 100644
--- a/layout/generic/nsSelection.cpp
+++ b/layout/generic/nsSelection.cpp
@@ -106,6 +106,31 @@ static void printRange(nsRange *aDomRange);
 
 //#define DEBUG_TABLE_SELECTION 1
 
+nsPeekOffsetStruct::nsPeekOffsetStruct(nsSelectionAmount aAmount,
+                                       nsDirection aDirection,
+                                       int32_t aStartOffset,
+                                       nscoord aDesiredX,
+                                       bool aJumpLines,
+                                       bool aScrollViewStop,
+                                       bool aIsKeyboardSelect,
+                                       bool aVisual,
+                                       EWordMovementType aWordMovementType)
+  : mAmount(aAmount)
+  , mDirection(aDirection)
+  , mStartOffset(aStartOffset)
+  , mDesiredX(aDesiredX)
+  , mWordMovementType(aWordMovementType)
+  , mJumpLines(aJumpLines)
+  , mScrollViewStop(aScrollViewStop)
+  , mIsKeyboardSelect(aIsKeyboardSelect)
+  , mVisual(aVisual)
+  , mResultContent()
+  , mResultFrame(nullptr)
+  , mContentOffset(0)
+  , mAttach(CARET_ASSOCIATE_BEFORE)
+{
+}
+
 struct CachedOffsetForFrame {
   CachedOffsetForFrame()
   : mCachedFrameOffset(0, 0) // nsPoint ctor
@@ -333,7 +358,7 @@ nsFrameSelection::nsFrameSelection()
   
   mMouseDoubleDownState = false;
   
-  mHint = HINTLEFT;
+  mHint = CARET_ASSOCIATE_BEFORE;
   mCaretBidiLevel = BIDI_LEVEL_UNDEFINED;
   mDragSelectingCells = false;
   mSelectingTableCellMode = 0;
@@ -364,6 +389,9 @@ nsFrameSelection::nsFrameSelection()
   mDelayedMouseEventClickCount = 0;
 }
 
+nsFrameSelection::~nsFrameSelection()
+{
+}
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(nsFrameSelection)
 
@@ -688,17 +716,17 @@ GetCellParent(nsINode *aDomNode)
     return nullptr;
 }
 
-nsFrameSelection::HINT
+CaretAssociationHint
 nsFrameSelection::GetHintForPosition(nsIContent* aContent, int32_t aOffset)
 {
-  HINT hint = HINTLEFT;
+  CaretAssociateHint hint = CARET_ASSOCIATE_BEFORE;
   if (!aContent || aOffset < 1) {
     return hint;
   }
   const nsTextFragment* text = aContent->GetText();
   if (text && text->CharAt(aOffset - 1) == '\n') {
     // Attach the caret to the next line if needed
-    hint = HINTRIGHT;
+    hint = CARET_ASSOCIATE_AFTER;
   }
   return hint;
 }
@@ -821,7 +849,7 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
             sel->Collapse(anchorFocusRange->GetStartParent(),
                           anchorFocusRange->StartOffset());
           }
-          mHint = HINTRIGHT;
+          mHint = CARET_ASSOCIATE_AFTER;
           sel->ScrollIntoView(nsISelectionController::SELECTION_FOCUS_REGION,
                               nsIPresShell::ScrollAxis(),
                               nsIPresShell::ScrollAxis(), scrollFlags);
@@ -837,7 +865,7 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
             sel->Collapse(anchorFocusRange->GetEndParent(),
                           anchorFocusRange->EndOffset());
           }
-          mHint = HINTLEFT;
+          mHint = CARET_ASSOCIATE_BEFORE;
           sel->ScrollIntoView(nsISelectionController::SELECTION_FOCUS_REGION,
                               nsIPresShell::ScrollAxis(),
                               nsIPresShell::ScrollAxis(), scrollFlags);
@@ -861,7 +889,7 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
 
   nsBidiLevel baseLevel = nsBidiPresUtils::GetFrameBaseLevel(frame);
   
-  HINT tHint(mHint); //temporary variable so we dont set mHint until it is necessary
+  CaretAssociateHint tHint(mHint); //temporary variable so we dont set mHint until it is necessary
   switch (aKeycode){
     case nsIDOMKeyEvent::DOM_VK_RIGHT : 
         InvalidateDesiredX();
@@ -907,19 +935,19 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
     {
       // For left/right, PeekOffset() sets pos.mResultFrame correctly, but does not set pos.mAttachForward,
       // so determine the hint here based on the result frame and offset:
-      // If we're at the end of a text frame, set the hint to HINTLEFT to indicate that we
+      // If we're at the end of a text frame, set the hint to ASSOCIATE_BEFORE to indicate that we
       // want the caret displayed at the end of this frame, not at the beginning of the next one.
       theFrame = pos.mResultFrame;
       theFrame->GetOffsets(frameStart, frameEnd);
       currentOffset = pos.mContentOffset;
       if (frameEnd == currentOffset && !(frameStart == 0 && frameEnd == 0))
-        tHint = HINTLEFT;
+        tHint = CARET_ASSOCIATE_BEFORE;
       else
-        tHint = HINTRIGHT;
+        tHint = CARET_ASSOCIATE_AFTER;
     } else {
       // For up/down and home/end, pos.mResultFrame might not be set correctly, or not at all.
       // In these cases, get the frame based on the content and hint returned by PeekOffset().
-      tHint = (HINT)pos.mAttachForward;
+      tHint = pos.mAttach;
       theFrame = GetFrameForNodeOffset(pos.mResultContent, pos.mContentOffset,
                                        tHint, &currentOffset);
       if (!theFrame)
@@ -958,7 +986,7 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
     sel->Collapse(sel->GetFocusNode(), sel->FocusOffset());
     // Note: 'frame' might be dead here.
     if (!isBRFrame) {
-      mHint = HINTLEFT; // We're now at the end of the frame to the left.
+      mHint = CARET_ASSOCIATE_BEFORE; // We're now at the end of the frame to the left.
     }
     result = NS_OK;
   }
@@ -1081,12 +1109,7 @@ Selection::SetInterlinePosition(bool aHintRight, ErrorResult& aRv)
     aRv.Throw(NS_ERROR_NOT_INITIALIZED); // Can't do selection
     return;
   }
-  nsFrameSelection::HINT hint;
-  if (aHintRight)
-    hint = nsFrameSelection::HINTRIGHT;
-  else
-    hint = nsFrameSelection::HINTLEFT;
-  mFrameSelection->SetHint(hint);
+  mFrameSelection->SetHint(aHintRight ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE);
 }
 
 NS_IMETHODIMP
@@ -1107,7 +1130,7 @@ Selection::GetInterlinePosition(ErrorResult& aRv)
     aRv.Throw(NS_ERROR_NOT_INITIALIZED); // Can't do selection
     return false;
   }
-  return (mFrameSelection->GetHint() == nsFrameSelection::HINTRIGHT);
+  return mFrameSelection->GetHint() == CARET_ASSOCIATE_AFTER;
 }
 
 nsPrevNextBidiLevels
@@ -1119,10 +1142,10 @@ nsFrameSelection::GetPrevNextBidiLevels(nsIContent *aNode,
 }
 
 nsPrevNextBidiLevels
-nsFrameSelection::GetPrevNextBidiLevels(nsIContent *aNode,
-                                        uint32_t    aContentOffset,
-                                        HINT        aHint,
-                                        bool        aJumpLines) const
+nsFrameSelection::GetPrevNextBidiLevels(nsIContent*        aNode,
+                                        uint32_t           aContentOffset,
+                                        CaretAssociateHint aHint,
+                                        bool               aJumpLines) const
 {
   // Get the level of the frames on each side
   nsIFrame    *currentFrame;
@@ -1269,11 +1292,11 @@ nsFrameSelection::MaintainSelection(nsSelectionAmount aAmount)
  * @param aKeycode is the keyboard event that moved the caret to the new position
  * @param aHint is the hint indicating in what logical direction the caret moved
  */
-void nsFrameSelection::BidiLevelFromMove(nsIPresShell* aPresShell,
-                                         nsIContent   *aNode,
-                                         uint32_t      aContentOffset,
-                                         uint32_t      aKeycode,
-                                         HINT          aHint)
+void nsFrameSelection::BidiLevelFromMove(nsIPresShell*      aPresShell,
+                                         nsIContent*        aNode,
+                                         uint32_t           aContentOffset,
+                                         uint32_t           aKeycode,
+                                         CaretAssociateHint aHint)
 {
   switch (aKeycode) {
 
@@ -1284,10 +1307,8 @@ void nsFrameSelection::BidiLevelFromMove(nsIPresShell* aPresShell,
       nsPrevNextBidiLevels levels = GetPrevNextBidiLevels(aNode, aContentOffset,
                                                           aHint, false);
 
-      if (HINTLEFT == aHint)
-        SetCaretBidiLevel(levels.mLevelBefore);
-      else
-        SetCaretBidiLevel(levels.mLevelAfter);
+      SetCaretBidiLevel(aHint == CARET_ASSOCIATE_BEFORE ?
+          levels.mLevelBefore : levels.mLevelAfter);
       break;
     }
       /*
@@ -1373,12 +1394,12 @@ nsFrameSelection::AdjustForMaintainedSelection(nsIContent *aContent,
 
 
 nsresult
-nsFrameSelection::HandleClick(nsIContent *aNewFocus,
-                              uint32_t    aContentOffset,
-                              uint32_t    aContentEndOffset,
-                              bool        aContinueSelection, 
-                              bool        aMultipleSelection,
-                              bool        aHint) 
+nsFrameSelection::HandleClick(nsIContent*        aNewFocus,
+                              uint32_t           aContentOffset,
+                              uint32_t           aContentEndOffset,
+                              bool               aContinueSelection,
+                              bool               aMultipleSelection,
+                              CaretAssociateHint aHint)
 {
   if (!aNewFocus)
     return NS_ERROR_INVALID_ARG;
@@ -1401,7 +1422,7 @@ nsFrameSelection::HandleClick(nsIContent *aNewFocus,
         AdjustForMaintainedSelection(aNewFocus, aContentOffset))
       return NS_OK; //shift clicked to maintained selection. rejected.
 
-    return TakeFocus(aNewFocus, aContentOffset, aContentEndOffset, HINT(aHint),
+    return TakeFocus(aNewFocus, aContentOffset, aContentEndOffset, aHint,
                      aContinueSelection, aMultipleSelection);
   }
   
@@ -1449,7 +1470,8 @@ nsFrameSelection::HandleDrag(nsIFrame *aFrame, nsPoint aPoint)
       amount = eSelectEndLine;
 
     int32_t offset;
-    nsIFrame* frame = GetFrameForNodeOffset(offsets.content, offsets.offset, HINTRIGHT, &offset);
+    nsIFrame* frame = GetFrameForNodeOffset(offsets.content, offsets.offset,
+        CARET_ASSOCIATE_AFTER, &offset);
 
     if (frame && amount == eSelectWord && direction == eDirPrevious) {
       // To avoid selecting the previous word when at start of word,
@@ -1472,7 +1494,7 @@ nsFrameSelection::HandleDrag(nsIFrame *aFrame, nsPoint aPoint)
   }
   
   HandleClick(offsets.content, offsets.offset, offsets.offset,
-              true, false, offsets.associateWithNext);
+              true, false, offsets.associate);
 }
 
 nsresult
@@ -1501,12 +1523,12 @@ nsFrameSelection::StopAutoScrollTimer()
 hard to go from nodes to frames, easy the other way!
  */
 nsresult
-nsFrameSelection::TakeFocus(nsIContent *aNewFocus,
-                            uint32_t    aContentOffset,
-                            uint32_t    aContentEndOffset,
-                            HINT        aHint,
-                            bool        aContinueSelection,
-                            bool        aMultipleSelection)
+nsFrameSelection::TakeFocus(nsIContent*        aNewFocus,
+                            uint32_t           aContentOffset,
+                            uint32_t           aContentEndOffset,
+                            CaretAssociateHint aHint,
+                            bool               aContinueSelection,
+                            bool               aMultipleSelection)
 {
   if (!aNewFocus)
     return NS_ERROR_NULL_POINTER;
@@ -1725,10 +1747,10 @@ nsFrameSelection::RepaintSelection(SelectionType aType) const
 }
  
 nsIFrame*
-nsFrameSelection::GetFrameForNodeOffset(nsIContent *aNode,
-                                        int32_t     aOffset,
-                                        HINT        aHint,
-                                        int32_t    *aReturnOffset) const
+nsFrameSelection::GetFrameForNodeOffset(nsIContent*        aNode,
+                                        int32_t            aOffset,
+                                        CaretAssociateHint aHint,
+                                        int32_t*           aReturnOffset) const
 {
   if (!aNode || !aReturnOffset || !mShell)
     return nullptr;
@@ -1745,15 +1767,16 @@ nsFrameSelection::GetFrameForNodeOffset(nsIContent *aNode,
     int32_t childIndex  = 0;
     int32_t numChildren = theNode->GetChildCount();
 
-    if (aHint == HINTLEFT)
+    if (aHint == CARET_ASSOCIATE_BEFORE)
     {
       if (aOffset > 0)
         childIndex = aOffset - 1;
       else
         childIndex = aOffset;
     }
-    else // HINTRIGHT
+    else
     {
+      NS_ASSERTION(aHint == CARET_ASSOCIATE_AFTER, "unknown direction");
       if (aOffset >= numChildren)
       {
         if (numChildren > 0)
@@ -1844,7 +1867,7 @@ nsFrameSelection::GetFrameForNodeOffset(nsIContent *aNode,
     return nullptr;
 
   // find the child frame containing the offset we want
-  returnFrame->GetChildFrameContainingOffset(*aReturnOffset, aHint == HINTRIGHT,
+  returnFrame->GetChildFrameContainingOffset(*aReturnOffset, aHint == CARET_ASSOCIATE_AFTER,
                                              &aOffset, &returnFrame);
   return returnFrame;
 }
@@ -1901,7 +1924,7 @@ nsFrameSelection::CommonPageMove(bool aForward,
 
   // place the caret
   HandleClick(offsets.content, offsets.offset,
-              offsets.offset, aExtend, false, true);
+              offsets.offset, aExtend, false, CARET_ASSOCIATE_AFTER);
 }
 
 nsresult
@@ -1984,7 +2007,7 @@ nsFrameSelection::SelectAll()
   }
   int32_t numChildren = rootContent->GetChildCount();
   PostReason(nsISelectionListener::NO_REASON);
-  return TakeFocus(rootContent, 0, numChildren, HINTLEFT, false, false);
+  return TakeFocus(rootContent, 0, numChildren, CARET_ASSOCIATE_BEFORE, false, false);
 }
 
 //////////END FRAMESELECTION
@@ -2977,7 +3000,7 @@ nsFrameSelection::SetAncestorLimiter(nsIContent *aLimiter)
       ClearNormalSelection();
       if (mAncestorLimiter) {
         PostReason(nsISelectionListener::NO_REASON);
-        TakeFocus(mAncestorLimiter, 0, 0, HINTLEFT, false, false);
+        TakeFocus(mAncestorLimiter, 0, 0, CARET_ASSOCIATE_BEFORE, false, false);
       }
     }
   }
@@ -3918,7 +3941,7 @@ Selection::GetPrimaryFrameForFocusNode(nsIFrame** aReturnFrame,
   if (!aOffsetUsed)
     aOffsetUsed = &frameOffset;
     
-  nsFrameSelection::HINT hint = mFrameSelection->GetHint();
+  CaretAssociationHint hint = mFrameSelection->GetHint();
 
   if (aVisual) {
     uint8_t caretBidiLevel = mFrameSelection->GetCaretBidiLevel();
@@ -5374,7 +5397,7 @@ Selection::GetSelectionEndPointGeometry(SelectionRegion aRegion, nsRect* aRect)
   // Return the rect relative to the frame, with zero width.
   if (isText) {
     aRect->x = pt.x;
-  } else if (mFrameSelection->GetHint() == nsFrameSelection::HINTLEFT) {
+  } else if (mFrameSelection->GetHint() == CARET_ASSOCIATE_BEFORE) {
     // It's the frame's right edge we're interested in.
     aRect->x = frame->GetRect().width;
   }
@@ -5801,18 +5824,6 @@ Selection::SelectionLanguageChange(bool aLangRTL)
     // the cursor is at a frame boundary, so use GetPrevNextBidiLevels to find the level of the characters
     //  before and after the cursor
     nsCOMPtr<nsIContent> focusContent = do_QueryInterface(GetFocusNode());
-    /*
-    nsFrameSelection::HINT hint;
-
-    if ((focusOffset == frameStart && level)        // beginning of an RTL frame
-        || (focusOffset == frameEnd && !level)) {   // end of an LTR frame
-      hint = nsFrameSelection::HINTRIGHT;
-    }
-    else {                                          // end of an RTL frame or beginning of an LTR frame
-      hint = nsFrameSelection::HINTLEFT;
-    }
-    mFrameSelection->SetHint(hint);
-    */
     nsPrevNextBidiLevels levels = mFrameSelection->
       GetPrevNextBidiLevels(focusContent, focusOffset, false);
       
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 3e04c2ea3d1d..c0b897a5d698 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -6294,7 +6294,8 @@ nsTextFrame::GetCharacterOffsetAtFramePointInternal(nsPoint aPoint,
 
   offsets.content = GetContent();
   offsets.offset = offsets.secondaryOffset = selectedOffset;
-  offsets.associateWithNext = mContentOffset == offsets.offset;
+  offsets.associate =
+    mContentOffset == offsets.offset ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE;
   return offsets;
 }
 
diff --git a/layout/svg/SVGTextFrame.cpp b/layout/svg/SVGTextFrame.cpp
index 908db5be85d5..2f1711f7567a 100644
--- a/layout/svg/SVGTextFrame.cpp
+++ b/layout/svg/SVGTextFrame.cpp
@@ -39,6 +39,7 @@
 #include "SVGPathElement.h"
 #include "SVGTextPathElement.h"
 #include "nsLayoutUtils.h"
+#include "nsFrameSelection.h"
 #include <algorithm>
 #include <cmath>
 #include <limits>
@@ -4050,7 +4051,7 @@ SVGTextFrame::SelectSubString(nsIContent* aContent,
   nsRefPtr<nsFrameSelection> frameSelection = GetFrameSelection();
 
   frameSelection->HandleClick(content, charnum, charnum + nchars,
-                              false, false, false);
+                              false, false, CARET_ASSOCIATE_BEFORE);
   return NS_OK;
 }
 
diff --git a/layout/xul/nsImageBoxFrame.cpp b/layout/xul/nsImageBoxFrame.cpp
index a68f91aa9b12..f99f52f20251 100644
--- a/layout/xul/nsImageBoxFrame.cpp
+++ b/layout/xul/nsImageBoxFrame.cpp
@@ -44,6 +44,7 @@
 #include "nsDisplayList.h"
 #include "ImageLayers.h"
 #include "ImageContainer.h"
+#include "nsIContent.h"
 
 #include "nsContentUtils.h"
 
diff --git a/layout/xul/nsListItemFrame.cpp b/layout/xul/nsListItemFrame.cpp
index ebb68fb30c64..54a16e4a1e0b 100644
--- a/layout/xul/nsListItemFrame.cpp
+++ b/layout/xul/nsListItemFrame.cpp
@@ -5,12 +5,14 @@
 
 #include "nsListItemFrame.h"
 
+#include <algorithm>
+
 #include "nsCOMPtr.h"
 #include "nsNameSpaceManager.h"
 #include "nsGkAtoms.h"
 #include "nsDisplayList.h"
 #include "nsBoxLayout.h"
-#include <algorithm>
+#include "nsIContent.h"
 
 nsListItemFrame::nsListItemFrame(nsIPresShell* aPresShell,
                                  nsStyleContext* aContext,
diff --git a/layout/xul/tree/nsTreeImageListener.cpp b/layout/xul/tree/nsTreeImageListener.cpp
index 2a8ab08fd38e..f559be042342 100644
--- a/layout/xul/tree/nsTreeImageListener.cpp
+++ b/layout/xul/tree/nsTreeImageListener.cpp
@@ -7,6 +7,7 @@
 #include "nsITreeBoxObject.h"
 #include "imgIRequest.h"
 #include "imgIContainer.h"
+#include "nsIContent.h"
 
 NS_IMPL_ISUPPORTS(nsTreeImageListener, imgINotificationObserver)