cc: Split out calcDrawEtc from drawLayers

cc/layer_tree_host_impl.h

Index: cc/layer_tree_host_impl.h
diff --git a/cc/layer_tree_host_impl.h b/cc/layer_tree_host_impl.h
index d4aa8f5a110950fbb61769d4188a6b9b2293efc7..836f51d84b9e8a27ad565ee6c2a87a1093632ebe 100644
--- a/cc/layer_tree_host_impl.h
+++ b/cc/layer_tree_host_impl.h
@@ -244,6 +244,9 @@ public:
     bool needsAnimateLayers() const { return m_needsAnimateLayers; }
     void setNeedsAnimateLayers() { m_needsAnimateLayers = true; }
 
+    bool needsUpdateLayers() const { return m_needsUpdateLayers; }
+    void setNeedsUpdateLayers() { m_needsUpdateLayers = true; }
+
     void setNeedsRedraw();
 
     void renderingStats(RenderingStats*) const;
@@ -294,6 +297,8 @@ protected:
     void animatePageScale(base::TimeTicks monotonicTime);
     void animateScrollbars(base::TimeTicks monotonicTime);
 
+    void updateLayers();
+
     // Exposed for testing.
     void calculateRenderSurfaceLayerList(LayerList&);
 
@@ -357,6 +362,7 @@ private:
 
     // If this is true, it is necessary to traverse the layer tree ticking the animators.
     bool m_needsAnimateLayers;
+    bool m_needsUpdateLayers;
     bool m_pinchGestureActive;
     gfx::Point m_previousPinchAnchor;