Handle ui::Layer's visibility using cc::Layer's m_isDrawable flag

cc/layer_impl.h

Index: cc/layer_impl.h
diff --git a/cc/layer_impl.h b/cc/layer_impl.h
index b02db83489562965d4f146ddbb4da6098fb24902..5cb934fa7738fb5a6809248c92b8adedee016ed6 100644
--- a/cc/layer_impl.h
+++ b/cc/layer_impl.h
@@ -118,6 +118,9 @@ public:
     bool forceRenderSurface() const { return m_forceRenderSurface; }
     void setForceRenderSurface(bool force) { m_forceRenderSurface = force; }
 
+    void setVisible(bool);
+    bool visible() const { return m_visible; }
+
     void setAnchorPoint(const gfx::PointF&);
     const gfx::PointF& anchorPoint() const { return m_anchorPoint; }
 
@@ -381,6 +384,7 @@ private:
 
     bool m_drawsContent;
     bool m_forceRenderSurface;
+    bool m_visible;
 
     // Set for the layer that other layers are fixed to.
     bool m_isContainerForFixedPositionLayers;