Only scroll on main if the targeted frames need to scroll on main

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

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
index b5775ab80f437659a1792d800a4e512b198bac16..21f1843e3a0f90482e5bcd56fa02b32dcd2c5951 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -41,6 +41,7 @@ namespace blink {
 using MainThreadScrollingReasons = uint32_t;
 
 class LocalFrame;
+class Frame;
 class FrameView;
 class GraphicsLayer;
 class Page;
@@ -94,9 +95,11 @@ class CORE_EXPORT ScrollingCoordinator final
   // Should be called whenever the root layer for the given frame view changes.
   void frameViewRootLayerDidChange(FrameView*);
 
-  MainThreadScrollingReasons mainThreadScrollingReasons() const;
-  bool shouldUpdateScrollLayerPositionOnMainThread() const {
-    return mainThreadScrollingReasons() != 0;
+  MainThreadScrollingReasons mainThreadScrollingReasons(LocalFrame*) const;

[pdr., 2016/12/13 05:51:17]

Nit: LocalFrame&
(const LocalFrame& if possible)

Similarly for the rest of this patch, switch from passing pointers to references
(const if possible).

[yigu, 2016/12/14 21:07:27]

Done.

+  MainThreadScrollingReasons mainThreadScrollingReasonsPerFrame(
+      LocalFrame*) const;
+  bool shouldUpdateScrollLayerPositionOnMainThread(LocalFrame* frame) const {
+    return mainThreadScrollingReasons(frame) != 0;
   }
 
   std::unique_ptr<WebScrollbarLayer> createSolidColorScrollbarLayer(
@@ -119,8 +122,9 @@ class CORE_EXPORT ScrollingCoordinator final
                                           const PaintLayer* parent);
   void updateClipParentForGraphicsLayer(GraphicsLayer* child,
                                         const PaintLayer* parent);
+  void updateSubFrameScrollOnMainReason();
 
-  String mainThreadScrollingReasonsAsText() const;
+  String mainThreadScrollingReasonsAsText(const Frame*) const;
   Region computeShouldHandleScrollGestureOnMainThreadRegion(
       const LocalFrame*,
       const IntPoint& frameLocation) const;