Don't schedule an animation during compositing dirty-bit setting unless needed.

Source/core/rendering/compositing/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 267 matching lines @@
 bool RenderLayerCompositor::canRender3DTransforms() const
 {
     return hasAcceleratedCompositing() && m_compositingReasonFinder.has3DTransformTrigger();
 }
 
 void RenderLayerCompositor::setCompositingLayersNeedRebuild()
 {
     // FIXME: crbug,com/332248 ideally this could be merged with setNeedsCompositingUpdate().
     if (inCompositingMode())
         m_compositingLayersNeedRebuild = true;
-
-    m_renderView.frameView()->scheduleAnimation();
+    page()->animator().scheduleVisualUpdate();
 }
 
 void RenderLayerCompositor::updateCompositingRequirementsState()
 {
     if (!m_needsUpdateCompositingRequirementsState)
         return;
 
     TRACE_EVENT0("blink_rendering,comp-scroll", "RenderLayerCompositor::updateCompositingRequirementsState");
 
     m_needsUpdateCompositingRequirementsState = false;
@@ skipping 78 matching lines @@
     case CompositingUpdateOnCompositedScroll:
         m_needsToUpdateLayerTreeGeometry = true;
         // FIXME: Ideally we'd be smarter about tracking dirtiness and wouldn't need a ForceUpdate here.
         m_pendingUpdateType = GraphicsLayerUpdater::ForceUpdate;
         break;
     case CompositingUpdateAfterCanvasContextChange:
         m_needsToUpdateLayerTreeGeometry = true;
         break;
     }
 
-    m_renderView.frameView()->scheduleAnimation();
+    page()->animator().scheduleVisualUpdate();
 }
 
 void RenderLayerCompositor::updateCompositingLayers()
 {
     TRACE_EVENT0("blink_rendering", "RenderLayerCompositor::updateCompositingLayers");
 
     // FIXME: We should carefully clean up the awkward early-exit semantics, balancing
     // between skipping unnecessary compositing updates and not incorrectly skipping
     // necessary updates.
 
     // Avoid updating the layers with old values. Compositing layers will be updated after the layout is finished.
     // FIXME: Can we assert that we never return here?
     if (m_renderView.needsLayout())
         return;
 
     lifecycle().advanceTo(DocumentLifecycle::InCompositingUpdate);
 
     updateCompositingLayersInternal();
 
     lifecycle().advanceTo(DocumentLifecycle::CompositingClean);
 
     DocumentAnimations::startPendingAnimations(m_renderView.document());
     ASSERT(m_renderView.document().lifecycle().state() == DocumentLifecycle::CompositingClean);
 }
 
+void RenderLayerCompositor::scheduleAnimationIfNeeded()
+{
+    if (hasUnresolvedDirtyBits())
+        m_renderView.frameView()->scheduleAnimation();

[abarth-chromium, 2014/03/19 18:04:57]

Should we early return here?

[chrishtr, 2014/03/19 18:16:00]

Done. Confirmed with enne@ that this is ok.

+
+    LocalFrame* localFrame = &m_renderView.frameView()->frame();
+    for (LocalFrame* child = localFrame->tree().firstChild(); child; child = child->tree().nextSibling()) {
+        if (child->contentRenderer()) {
+            RenderLayerCompositor* childCompositor = child->contentRenderer()->compositor();
+            if (childCompositor)
+                childCompositor->scheduleAnimationIfNeeded();

[abarth-chromium, 2014/03/19 18:04:57]

Rather than using recursion here, we can use frame->tree().traverseNext(...) to
make this walk into a simple loop.  Once we do that, we can early return once we
find some dirty bits.

[chrishtr, 2014/03/19 18:16:00]

Done.

+        }
+    }
+}
+
+bool RenderLayerCompositor::hasUnresolvedDirtyBits()
+{
+    return m_needsToRecomputeCompositingRequirements || m_compositingLayersNeedRebuild || m_needsToUpdateLayerTreeGeometry || m_needsUpdateCompositingRequirementsState || m_pendingUpdateType != GraphicsLayerUpdater::DoNotForceUpdate;
+}
+
 void RenderLayerCompositor::updateCompositingLayersInternal()
 {
     if (isMainFrame() && m_renderView.frameView())
         finishCompositingUpdateForFrameTree(&m_renderView.frameView()->frame());
 
     if (m_forceCompositingMode && !m_compositing)
         enableCompositingMode(true);
 
     if (!m_needsToRecomputeCompositingRequirements && !m_compositing)
         return;
@@ skipping 1819 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "LocalFrame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore