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

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index 1ec3750969ebc2b8613ca5c6ebce60d59bc70495..9b97aca050812d254b634c7c898c3c6288c7caba 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -285,8 +285,7 @@ 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()
@@ -385,7 +384,7 @@ void RenderLayerCompositor::setNeedsCompositingUpdate(CompositingUpdateType upda
         break;
     }
 
-    m_renderView.frameView()->scheduleAnimation();
+    page()->animator().scheduleVisualUpdate();
 }
 
 void RenderLayerCompositor::updateCompositingLayers()
@@ -411,6 +410,26 @@ void RenderLayerCompositor::updateCompositingLayers()
     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())