Reduce compositing update in Silk's toggle_drawer by 20%

Source/core/rendering/compositing/GraphicsLayerUpdater.h

Index: Source/core/rendering/compositing/GraphicsLayerUpdater.h
diff --git a/Source/core/rendering/compositing/GraphicsLayerUpdater.h b/Source/core/rendering/compositing/GraphicsLayerUpdater.h
index 9b9658a2762919cade645aef2298c6e18d87f639..745294acdc43931deffe1d605f188257ad9401d8 100644
--- a/Source/core/rendering/compositing/GraphicsLayerUpdater.h
+++ b/Source/core/rendering/compositing/GraphicsLayerUpdater.h
@@ -41,11 +41,16 @@ public:
     explicit GraphicsLayerUpdater(RenderView&);
     ~GraphicsLayerUpdater();
 
-    void updateRecursive(RenderLayer&);
-    void rebuildTree(RenderLayer&, Vector<GraphicsLayer*>& childLayersOfEnclosingLayer, int depth);
+    enum UpdateType {
+        DoNotForceUpdate,
+        ForceUpdate,
+    };
+
+    void updateRecursive(RenderLayer&, UpdateType);
+    void rebuildTree(RenderLayer&, UpdateType, Vector<GraphicsLayer*>& childLayersOfEnclosingLayer, int depth);
 
 private:
-    void update(RenderLayer&);
+    UpdateType update(RenderLayer&, UpdateType);
 
     RenderView& m_renderView;