Fix touch event flag may not be updated correctly by transform which causes no layout

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 833dd7e51505056c4ac95379d51e5bbcc2a97643..705ec01948bcc73052547dbbe8ef03a592c5f73b 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -128,6 +128,14 @@ void ScrollingCoordinator::notifyGeometryChanged() {
   m_shouldScrollOnMainThreadDirty = true;
 }
 
+void ScrollingCoordinator::checkTransformChangedDueToTouchEvent(
+    const PaintLayer* layer) {
+  if (layer->enclosingNode()->hasBlockingEventListeners(
+          EventTypeNames::touchstart) ||
+      layer->enclosingNode()->hasBlockingEventListeners(
+          EventTypeNames::touchmove))

[majidvp, 2017/01/04 16:48:51]

After some more thinking I don't think this optimization is correct.

In particular, it possible for a paint layer to have touch rects even if does
not have touch event
handlers as we have an optimization where we report a touch rect on an ancestor
non-composited
scroller paint layer. In such a case, if a transform changes for this layer,
then we should
recompute the touch rects.


So perhaps instead of looking for existence of touch event handler the right
test is to check if
this layer (or layout object) has contributed a touch rect. This information is
available inside
|ScrollingCoordinator::computeTouchEventTargetRects| but it is not kept around.

[yigu, 2017/01/05 14:05:43]

As we discussed, we now optimize by walking up the layoutbox tree to see whether
the enclosinglayer is in the layerswithrects set.

+    m_touchEventTargetRectsAreDirty = true;
+}
 void ScrollingCoordinator::notifyOverflowUpdated() {
   m_scrollGestureRegionIsDirty = true;
 }