diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index bcce3c17c88b..49a8a620cf3c 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -10408,7 +10408,7 @@ nsSize nsFrame::GetXULMinSize(nsBoxLayoutState& aState) {
   // get our size in CSS.
   bool widthSet, heightSet;
   bool completelyRedefined =
-      nsIFrame::AddXULMinSize(this, size, widthSet, heightSet);
+      nsIFrame::AddXULMinSize(aState, this, size, widthSet, heightSet);
 
   // Refresh our caches with new sizes.
   if (!completelyRedefined) {
diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index becd5b51d4f6..18aad0692620 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -1665,7 +1665,7 @@ nsSize nsXULScrollFrame::GetXULMinSize(nsBoxLayoutState& aState) {
 
   AddBorderAndPadding(min);
   bool widthSet, heightSet;
-  nsIFrame::AddXULMinSize(this, min, widthSet, heightSet);
+  nsIFrame::AddXULMinSize(aState, this, min, widthSet, heightSet);
   return min;
 }
 
diff --git a/layout/generic/nsIFrame.h b/layout/generic/nsIFrame.h
index ca7afd4ae012..402030fd3412 100644
--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -3848,8 +3848,8 @@ class nsIFrame : public nsQueryFrame {
 
   static bool AddXULPrefSize(nsIFrame* aBox, nsSize& aSize, bool& aWidth,
                              bool& aHeightSet);
-  static bool AddXULMinSize(nsIFrame* aBox, nsSize& aSize, bool& aWidth,
-                            bool& aHeightSet);
+  static bool AddXULMinSize(nsBoxLayoutState& aState, nsIFrame* aBox,
+                            nsSize& aSize, bool& aWidth, bool& aHeightSet);
   static bool AddXULMaxSize(nsIFrame* aBox, nsSize& aSize, bool& aWidth,
                             bool& aHeightSet);
   static bool AddXULFlex(nsIFrame* aBox, nscoord& aFlex);
diff --git a/layout/xul/grid/nsGrid.cpp b/layout/xul/grid/nsGrid.cpp
index ebcc35aa36c6..95a9a8012a03 100644
--- a/layout/xul/grid/nsGrid.cpp
+++ b/layout/xul/grid/nsGrid.cpp
@@ -796,7 +796,7 @@ nscoord nsGrid::GetMinRowHeight(nsBoxLayoutState& aState, int32_t aIndex,
   if (box) {
     bool widthSet, heightSet;
     nsSize cssSize(-1, -1);
-    nsIFrame::AddXULMinSize(box, cssSize, widthSet, heightSet);
+    nsIFrame::AddXULMinSize(aState, box, cssSize, widthSet, heightSet);
 
     row->mMin = GET_HEIGHT(cssSize, aIsHorizontal);
 
diff --git a/layout/xul/nsBox.cpp b/layout/xul/nsBox.cpp
index 675cba7f9ece..ab3a807c40e6 100644
--- a/layout/xul/nsBox.cpp
+++ b/layout/xul/nsBox.cpp
@@ -229,7 +229,7 @@ nsSize nsBox::GetXULMinSize(nsBoxLayoutState& aState) {
 
   AddBorderAndPadding(min);
   bool widthSet, heightSet;
-  nsIFrame::AddXULMinSize(this, min, widthSet, heightSet);
+  nsIFrame::AddXULMinSize(aState, this, min, widthSet, heightSet);
   return min;
 }
 
@@ -421,30 +421,28 @@ static nscoord GetScrollbarWidthNoTheme(nsIFrame* aBox) {
   }
 }
 
-bool nsIFrame::AddXULMinSize(nsIFrame* aBox,
+bool nsIFrame::AddXULMinSize(nsBoxLayoutState& aState, nsIFrame* aBox,
                              nsSize& aSize, bool& aWidthSet, bool& aHeightSet) {
   aWidthSet = false;
   aHeightSet = false;
 
   bool canOverride = true;
 
-  nsPresContext* pc = aBox->PresContext();
-
   // See if a native theme wants to supply a minimum size.
   const nsStyleDisplay* display = aBox->StyleDisplay();
   if (display->HasAppearance()) {
-    nsITheme* theme = pc->GetTheme();
-    if (theme && theme->ThemeSupportsWidget(pc, aBox,
+    nsITheme* theme = aState.PresContext()->GetTheme();
+    if (theme && theme->ThemeSupportsWidget(aState.PresContext(), aBox,
                                             display->mAppearance)) {
       LayoutDeviceIntSize size;
-      theme->GetMinimumWidgetSize(pc, aBox,
+      theme->GetMinimumWidgetSize(aState.PresContext(), aBox,
                                   display->mAppearance, &size, &canOverride);
       if (size.width) {
-        aSize.width = pc->DevPixelsToAppUnits(size.width);
+        aSize.width = aState.PresContext()->DevPixelsToAppUnits(size.width);
         aWidthSet = true;
       }
       if (size.height) {
-        aSize.height = pc->DevPixelsToAppUnits(size.height);
+        aSize.height = aState.PresContext()->DevPixelsToAppUnits(size.height);
         aHeightSet = true;
       }
     } else {
diff --git a/layout/xul/nsBoxFrame.cpp b/layout/xul/nsBoxFrame.cpp
index eb119cd35d6a..b55f55a11fa3 100644
--- a/layout/xul/nsBoxFrame.cpp
+++ b/layout/xul/nsBoxFrame.cpp
@@ -606,7 +606,8 @@ nsSize nsBoxFrame::GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) {
 
   // if the size was not completely redefined in CSS then ask our children
   bool widthSet, heightSet;
-  if (!nsIFrame::AddXULMinSize(this, size, widthSet, heightSet)) {
+  if (!nsIFrame::AddXULMinSize(aBoxLayoutState, this, size, widthSet,
+                               heightSet)) {
     if (mLayoutManager) {
       nsSize layoutSize = mLayoutManager->GetXULMinSize(this, aBoxLayoutState);
       if (!widthSet) size.width = layoutSize.width;
diff --git a/layout/xul/nsImageBoxFrame.cpp b/layout/xul/nsImageBoxFrame.cpp
index 8d3df8718a64..ceb9753ec6b8 100644
--- a/layout/xul/nsImageBoxFrame.cpp
+++ b/layout/xul/nsImageBoxFrame.cpp
@@ -736,7 +736,7 @@ nsSize nsImageBoxFrame::GetXULMinSize(nsBoxLayoutState& aState) {
   DISPLAY_MIN_SIZE(this, size);
   AddBorderAndPadding(size);
   bool widthSet, heightSet;
-  nsIFrame::AddXULMinSize(this, size, widthSet, heightSet);
+  nsIFrame::AddXULMinSize(aState, this, size, widthSet, heightSet);
   return size;
 }
 
diff --git a/layout/xul/nsScrollbarFrame.cpp b/layout/xul/nsScrollbarFrame.cpp
index e1f4e74fb74b..3fdc025a794c 100644
--- a/layout/xul/nsScrollbarFrame.cpp
+++ b/layout/xul/nsScrollbarFrame.cpp
@@ -163,47 +163,39 @@ nsIScrollbarMediator* nsScrollbarFrame::GetScrollbarMediator() {
 }
 
 nsresult nsScrollbarFrame::GetXULMargin(nsMargin& aMargin) {
+  nsresult rv = NS_ERROR_FAILURE;
   aMargin.SizeTo(0, 0, 0, 0);
 
-  const bool overlayScrollbars =
-      !!LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars);
-
-  const bool horizontal = IsXULHorizontal();
-  bool didSetMargin = false;
-
-  if (overlayScrollbars) {
-    nsSize minSize;
-    bool widthSet = false;
-    bool heightSet = false;
-    AddXULMinSize(this, minSize, widthSet, heightSet);
-    if (horizontal) {
-      if (heightSet) {
-        aMargin.top = -minSize.height;
-        didSetMargin = true;
-      }
-    } else {
-      if (widthSet) {
-        aMargin.left = -minSize.width;
-        didSetMargin = true;
+  if (LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars) != 0) {
+    nsPresContext* presContext = PresContext();
+    nsITheme* theme = presContext->GetTheme();
+    if (theme && theme->ThemeSupportsWidget(presContext, this,
+                                            StyleAppearance::Scrollbar)) {
+      LayoutDeviceIntSize size;
+      bool isOverridable;
+      theme->GetMinimumWidgetSize(presContext, this, StyleAppearance::Scrollbar,
+                                  &size, &isOverridable);
+      if (IsXULHorizontal()) {
+        aMargin.top = -presContext->DevPixelsToAppUnits(size.height);
+      } else {
+        aMargin.left = -presContext->DevPixelsToAppUnits(size.width);
       }
+      rv = NS_OK;
     }
   }
 
-  if (!didSetMargin) {
-    DebugOnly<nsresult> rv = nsBox::GetXULMargin(aMargin);
-    // TODO(emilio): Should probably not be fallible, it's not like anybody
-    // cares about the return value anyway.
-    MOZ_ASSERT(NS_SUCCEEDED(rv), "nsBox::GetXULMargin can't really fail");
+  if (NS_FAILED(rv)) {
+    rv = nsBox::GetXULMargin(aMargin);
   }
 
-  if (!horizontal) {
+  if (NS_SUCCEEDED(rv) && !IsXULHorizontal()) {
     nsIScrollbarMediator* scrollFrame = GetScrollbarMediator();
     if (scrollFrame && !scrollFrame->IsScrollbarOnRight()) {
       std::swap(aMargin.left, aMargin.right);
     }
   }
 
-  return NS_OK;
+  return rv;
 }
 
 void nsScrollbarFrame::SetIncrementToLine(int32_t aDirection) {
diff --git a/layout/xul/nsTextBoxFrame.cpp b/layout/xul/nsTextBoxFrame.cpp
index eaba4e730392..cf970d27af36 100644
--- a/layout/xul/nsTextBoxFrame.cpp
+++ b/layout/xul/nsTextBoxFrame.cpp
@@ -1080,7 +1080,7 @@ nsSize nsTextBoxFrame::GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) {
 
   AddBorderAndPadding(size);
   bool widthSet, heightSet;
-  nsIFrame::AddXULMinSize(this, size, widthSet, heightSet);
+  nsIFrame::AddXULMinSize(aBoxLayoutState, this, size, widthSet, heightSet);
 
   return size;
 }
diff --git a/layout/xul/tree/nsTreeBodyFrame.cpp b/layout/xul/tree/nsTreeBodyFrame.cpp
index 57e398a88821..f2f9ed7d7fe5 100644
--- a/layout/xul/tree/nsTreeBodyFrame.cpp
+++ b/layout/xul/tree/nsTreeBodyFrame.cpp
@@ -192,7 +192,7 @@ nsSize nsTreeBodyFrame::GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) {
 
   AddBorderAndPadding(min);
   bool widthSet, heightSet;
-  nsIFrame::AddXULMinSize(this, min, widthSet, heightSet);
+  nsIFrame::AddXULMinSize(aBoxLayoutState, this, min, widthSet, heightSet);
 
   return min;
 }
diff --git a/toolkit/themes/mobile/global/scrollbars.css b/toolkit/themes/mobile/global/scrollbars.css
index b9692f384866..c81421e82d61 100644
--- a/toolkit/themes/mobile/global/scrollbars.css
+++ b/toolkit/themes/mobile/global/scrollbars.css
@@ -20,7 +20,10 @@ xul|scrollbar {
   display: block;
 }
 
+/* Scrollbar code will reset the margin to the correct side depending on
+   where layout actually puts the scrollbar */
 xul|scrollbar[orient="vertical"] {
+  margin-left: -6px;
   min-width: 6px;
   max-width: 6px;
 }
@@ -32,6 +35,7 @@ xul|scrollbar[orient="vertical"] xul|thumb {
 }
 
 xul|scrollbar[orient="horizontal"] {
+  margin-top: -6px;
   min-height: 6px;
   max-height: 6px;
 }