Bug 1319560 Part 2: Add a nsLayoutUtils::FrameForPointFlags value to only retrieve visible frames. r=mattwoodrow

MozReview-Commit-ID: 1mNIXdyBkw4

--HG--
extra : rebase_source : c4f9bb9dc920078bca8a33f95c006ecc5903be8a

layout/base/nsLayoutUtils.cpp

@@ -3167,6 +3167,7 @@ nsLayoutUtils::GetFramesForArea(nsIFrame* aFrame, const nsRect& aRect,
 #endif
 
   nsDisplayItem::HitTestState hitTestState;
+  builder.SetHitTestShouldStopAtFirstOpaque(aFlags & ONLY_VISIBLE);
   list.HitTest(&builder, aRect, &hitTestState, &aOutFrames);
   list.DeleteAll();
   return NS_OK;

layout/base/nsLayoutUtils.h

@@ -803,7 +803,11 @@ public:
     /**
      * When set, return only content in the same document as aFrame.
      */
-    IGNORE_CROSS_DOC = 0x04
+    IGNORE_CROSS_DOC = 0x04,
+    /**
+     * When set, return only content that is actually visible.
+     */
+    ONLY_VISIBLE = 0x08
   };
 
   /**