Remove CompositingUpdateOnScroll

This CL teaches the callers of CompositingUpdateOnScroll how to do partial
compositing updates. Now that they're smarter, we can use
CompositingUpdateAfterCompositingInputChange and we don't need
CompositingUpdateOnScroll anymore.

Review URL: https://codereview.chromium.org/326443002

git-svn-id: svn://svn.chromium.org/blink/trunk@175729 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/frame/FrameView.cpp

@@ -1681,14 +1681,12 @@ void FrameView::updateLayersAndCompositingAfterScrollIfNeeded()
     // layout.
     if (!m_nestedLayoutCount) {
         updateWidgetPositions();
-        if (RenderView* renderView = this->renderView())
+        if (RenderView* renderView = this->renderView()) {
             renderView->layer()->updateLayerPositionsAfterDocumentScroll();
+            renderView->layer()->setNeedsToUpdateAncestorDependentProperties();
+            renderView->compositor()->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
+        }
     }
-
-    // Compositing layers may change after scrolling.
-    // FIXME: Maybe no longer needed after we land squashing and kill overlap testing?
-    if (RenderView* renderView = this->renderView())
-        renderView->compositor()->setNeedsCompositingUpdate(CompositingUpdateOnScroll);
 }
 
 void FrameView::updateFixedElementPaintInvalidationRectsAfterScroll()

third_party/WebKit/Source/core/rendering/RenderLayerScrollableArea.cpp

@@ -1491,7 +1491,8 @@ void RenderLayerScrollableArea::updateCompositingLayersAfterScroll()
             box().compositedLayerMapping()->setNeedsGraphicsLayerUpdate();
             compositor->setNeedsCompositingUpdate(CompositingUpdateOnCompositedScroll);
         } else {
-            compositor->setNeedsCompositingUpdate(CompositingUpdateOnScroll);
+            layer()->setNeedsToUpdateAncestorDependentProperties();
+            compositor->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
         }
     }
 }

third_party/WebKit/Source/core/rendering/compositing/RenderLayerCompositor.h

@@ -50,7 +50,6 @@ enum CompositingUpdateType {
     CompositingUpdateOnCompositedScroll,
     CompositingUpdateAfterCompositingInputChange,
     CompositingUpdateAfterLayout,
-    CompositingUpdateOnScroll,
 };
 
 enum CompositingStateTransitionType {