Reduce compositing update in Silk's toggle_drawer by 20%

Source/core/rendering/compositing/RenderLayerCompositor.h

Index: Source/core/rendering/compositing/RenderLayerCompositor.h
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.h b/Source/core/rendering/compositing/RenderLayerCompositor.h
index a23086908e655b10e03db20f6da2f003e784c50a..9c75da1654c85fde4350071a1481c35518f406b9 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.h
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.h
@@ -29,6 +29,7 @@
 #include "core/page/ChromeClient.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/compositing/CompositingReasonFinder.h"
+#include "core/rendering/compositing/GraphicsLayerUpdater.h"
 #include "platform/graphics/GraphicsLayerClient.h"
 #include "wtf/HashMap.h"
 
@@ -340,6 +341,7 @@ private:
     // FIXME: This should absolutely not be mutable.
     mutable bool m_needsToRecomputeCompositingRequirements;
     bool m_needsToUpdateLayerTreeGeometry;
+    GraphicsLayerUpdater::UpdateType m_pendingUpdateType;
 
     bool m_compositing;
     bool m_compositingLayersNeedRebuild;