If a compositing update is declared as needed, scheduleAnimation should be triggered.

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index 1b8d51ed94b5ba2d93e2f6ad083ed0b1dd0fef50..d060cc30001480e110e8d6147f1e5dc0f8dee687 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -296,8 +296,11 @@ bool RenderLayerCompositor::canRender3DTransforms() const
 
 void RenderLayerCompositor::setCompositingLayersNeedRebuild(bool needRebuild)
 {
+    // FIXME: this code needs to be carefully merged with setNeedsCompositingUpdate.

[jamesr, 2014/02/11 01:50:14]

I don't really understand what this comment is trying to convey.  Is there a bug
on this issue? Could you just have a reference to that bug here?

     if (inCompositingMode())
         m_compositingLayersNeedRebuild = needRebuild;
+
+    m_renderView->frameView()->scheduleAnimation();
 }
 
 void RenderLayerCompositor::updateCompositingRequirementsState()
@@ -385,10 +388,7 @@ void RenderLayerCompositor::setNeedsCompositingUpdate(CompositingUpdateType upda
         break;
     }
 
-    // FIXME: some senior devs are suggesting that we need to always schedule a frame here.
-    // but we do seem to reach this point in code when frames are unnecessary and
-    // we need to resolve those instances before initiating a frame here, otherwise
-    // performance will regress by forcing unnecessary frames.
+    m_renderView->frameView()->scheduleAnimation();
 }
 
 void RenderLayerCompositor::updateCompositingLayers()