Correct touch rect hit-test against iframe with scrolled content

Source/core/layout/LayoutPart.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 166 matching lines @@
             if (result.hitTestRequest().listBased()) {
                 result.append(childFrameResult);
             } else if (isInsideChildFrame) {
                 // Force the result not to be cacheable because the parent
                 // frame should not cache this result; as it won't be notified of
                 // changes in the child.
                 childFrameResult.setCacheable(false);
                 result = childFrameResult;
             }
 
-            if (isInsideChildFrame)
+            // Don't trust |isInsideChildFrame|. Returns true only when the hit test
+            // point/rect is totally within the iframe, i.e. nodeAtPointOverWidget()
+            // also returns true.
+            // Use a temparory HitTestResult because we don't want to collect the
+            // iframe element itself if the hit-test rect is totally within the iframe.
+            HitTestResult pointOverWidgetResult = result;
+            if (isInsideChildFrame
+                && nodeAtPointOverWidget(pointOverWidgetResult, locationInContainer, accumulatedOffset, action))

[Rick Byers, 2015/09/08 15:12:33]

If this returns false, we'll run it again below.  We only ever need to run
nodeAtPointOverWidget once, right?

[Yufeng Shen (Slow to review), 2015/09/08 18:44:53]

right, optimized so that nodeAtPointOverWidget() will only be called once.

                 return true;
+
         }
     }
 
     return nodeAtPointOverWidget(result, locationInContainer, accumulatedOffset, action);
 }
 
 CompositingReasons LayoutPart::additionalCompositingReasons() const
 {
     if (requiresAcceleratedCompositing())
         return CompositingReasonIFrame;
@@ skipping 139 matching lines @@
     if (widget() && widget()->isFrameView()) {
         FrameView* childFrameView = toFrameView(widget());
         PaintInvalidationState childViewPaintInvalidationState(*childFrameView->layoutView(), paintInvalidationState);
         toFrameView(widget())->invalidateTreeIfNeeded(childViewPaintInvalidationState);
     }
 
     LayoutReplaced::invalidatePaintOfSubtreesIfNeeded(paintInvalidationState);
 }
 
 }