Add more specific metrics for main thread scrolling reasons

third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
index 762ab7bff80d818af0700a35f89fe35f65b5c10f..ce0018e27f918cbca2c241f3b048de4c3944866d 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
@@ -28,6 +28,7 @@
 
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
+#include "core/page/Page.h"
 #include "core/paint/PaintLayer.h"
 #include "core/paint/PaintLayerStackingNode.h"
 #include "core/paint/PaintLayerStackingNodeIterator.h"
@@ -250,6 +251,10 @@ void CompositingRequirementsUpdater::updateRecursive(
   CompositingReasons directReasons =
       m_compositingReasonFinder.directReasons(layer);
 
+  if (ScrollingCoordinator* scrollingCoordinator =
+          m_layoutView.document().page()->scrollingCoordinator())
+    updateMainThreadScrollingReasonsFromStyle(layer, scrollingCoordinator);

[bokan, 2016/12/14 13:28:58]

No need to pass in ScrollingCoordinator, just get it inside the method.

[yigu, 2016/12/14 21:17:32]

Done.

+
   // Video is special. It's the only PaintLayer type that can both have
   // PaintLayer children and whose children can't use its backing to render
   // into. These children (the controls) always need to be promoted into their
@@ -544,4 +549,24 @@ void CompositingRequirementsUpdater::updateRecursive(
   layer->setCompositingReasons(reasonsToComposite);
 }
 
+// Check if current layer has layout object that contains properties that cause
+// main thread scrolling.
+void CompositingRequirementsUpdater::updateMainThreadScrollingReasonsFromStyle(
+    const PaintLayer* layer,
+    ScrollingCoordinator* scrollingCoordinator) const {
+  // If current layer has opacity and has not been recorded, add the layer into
+  // frameView and vice versa.
+  if (!layer || !layer->getScrollableArea())
+    return;
+  if (layer->compositesWithOpacity() !=
+      layer->getScrollableArea()->hasMainThreadScrollingReason(
+          MainThreadScrollingReason::kHasOpacity)) {
+    layer->getScrollableArea()->flipMainThreadScrollingReason(
+        MainThreadScrollingReason::kHasOpacity);
+
+    scrollingCoordinator->adjustMainThreadReasonsFromStyle(
+        MainThreadScrollingReason::kHasOpacity, layer->compositesWithOpacity());
+  }
+}
+
 }  // namespace blink