Set up clip and scroll parents on the blink side.

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 7a3005971a154c0687a97e6238578ab263d186e4..7002305d0d013ee7d556ea7a4067273d17515762 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -288,6 +288,10 @@ void ScrollingCoordinator::scrollableAreaScrollbarLayerDidChange(ScrollableArea*
 
 bool ScrollingCoordinator::scrollableAreaScrollLayerDidChange(ScrollableArea* scrollableArea)
 {
+    TRACE_EVENT_INSTANT2("comp-scroll", "ScrollingCoordinator::scrollableAreaScrollLayerDidChange",
+        "width", scrollableArea->scrollableAreaBoundingBox().width(),
+        "height", scrollableArea->scrollableAreaBoundingBox().height());
+
     GraphicsLayer* scrollLayer = scrollLayerForScrollableArea(scrollableArea);
     if (scrollLayer) {
         bool isMainFrame = isForMainFrame(scrollableArea);
@@ -405,6 +409,46 @@ void ScrollingCoordinator::touchEventTargetRectsDidChange(const Document*)
     setTouchEventTargetRects(touchEventTargetRects);
 }
 
+void ScrollingCoordinator::updateScrollParentForLayer(RenderLayer* child, RenderLayer* parent)
+{
+    if (!child || !child->backing())
+        return;
+
+    WebLayer* childWebLayer = scrollingWebLayerForGraphicsLayer(child->layerForScrollChild());
+    if (!childWebLayer)
+        return;
+
+    WebLayer* scrollParentWebLayer = 0;
+    if (parent && parent->backing())
+        scrollParentWebLayer = scrollingWebLayerForGraphicsLayer(parent->backing()->parentForSublayers());
+
+    TRACE_EVENT_INSTANT2("comp-scroll2", "ScrollingCoordinator::updateScrollParentForLayer",

[enne (OOO), 2013/08/22 20:54:30]

Would this trace event be better on the cc side where you could only do it when
the scroll parent changed? Same question for a bunch of other places.

Also, comp-scroll2??

+        "childId", childWebLayer->id(),
+        "ancestorId", scrollParentWebLayer ? scrollParentWebLayer->id() : -1);

[enne (OOO), 2013/08/22 20:54:30]

Ids start at 1, so you could say 0.

+
+    childWebLayer->setScrollParent(scrollParentWebLayer);
+}
+
+void ScrollingCoordinator::updateClipParentForLayer(RenderLayer* child, RenderLayer* parent)
+{
+    if (!child || !child->backing())
+        return;
+
+    WebLayer* childWebLayer = scrollingWebLayerForGraphicsLayer(child->backing()->graphicsLayer());
+    if (!childWebLayer)
+        return;
+
+    WebLayer* clipParentWebLayer = 0;
+    if (parent && parent->backing())
+        clipParentWebLayer = scrollingWebLayerForGraphicsLayer(parent->backing()->parentForSublayers());
+
+    TRACE_EVENT_INSTANT2("comp-scroll", "ScrollingCoordinator::updateClipParentForLayer",
+        "childId", childWebLayer->id(),
+        "ancestorId", clipParentWebLayer ? clipParentWebLayer->id() : -1);
+
+    childWebLayer->setClipParent(clipParentWebLayer);
+}
+
 void ScrollingCoordinator::setWheelEventHandlerCount(unsigned count)
 {
     if (WebLayer* scrollLayer = scrollingWebLayerForScrollableArea(m_page->mainFrame()->view()))
@@ -419,8 +463,12 @@ void ScrollingCoordinator::recomputeWheelEventHandlerCountForFrameView(FrameView
 
 void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons reasons)
 {
-    if (WebLayer* scrollLayer = scrollingWebLayerForScrollableArea(m_page->mainFrame()->view()))
+    if (WebLayer* scrollLayer = scrollingWebLayerForScrollableArea(m_page->mainFrame()->view())) {
+        TRACE_EVENT_INSTANT2("impl-scroll", "ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread",
+            "layerId", scrollLayer->id(),
+            "reasons", reasons);
         scrollLayer->setShouldScrollOnMainThread(reasons);
+    }
 }
 
 void ScrollingCoordinator::pageDestroyed()