Correct touch rect hit-test against iframe with scrolled content

Source/core/layout/LayoutPart.cpp

Index: Source/core/layout/LayoutPart.cpp
diff --git a/Source/core/layout/LayoutPart.cpp b/Source/core/layout/LayoutPart.cpp
index 81cd54bf1e1324ecab7af1dc2023757b8c868bea..c811419bd389d072f80ca40667429862e72b5e86 100644
--- a/Source/core/layout/LayoutPart.cpp
+++ b/Source/core/layout/LayoutPart.cpp
@@ -184,8 +184,16 @@ bool LayoutPart::nodeAtPoint(HitTestResult& result, const HitTestLocation& locat
                 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;
+
         }
     }