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

ui/compositor/layer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 323 matching lines @@
   void CreateWebLayer();
   void RecomputeTransform();
   void RecomputeDrawsContentAndUVRect();
 
   // Set all filters which got applied to the layer.
   void SetLayerFilters();
 
   // Set all filters which got applied to the layer background.
   void SetLayerBackgroundFilters();
 
+  void UpdateIsDrawn();
+
   const LayerType type_;
 
   Compositor* compositor_;
 
   scoped_refptr<ui::Texture> texture_;
 
   Layer* parent_;
 
   // This layer's children, in bottom-to-top stacking order.
   std::vector<Layer*> children_;
 
   gfx::Transform transform_;
 
   gfx::Rect bounds_;
 
   // Visibility of this layer. See SetVisible/IsDrawn for more details.
   bool visible_;
 
+  // Computed based on the visibility of this layer and its ancestors.
+  bool is_drawn_;
+
   bool force_render_surface_;
 
   bool fills_bounds_opaquely_;
 
   // If true the layer is always up to date.
   bool layer_updated_externally_;
 
   // Union of damaged rects, in pixel coordinates, to be used when
   // compositor is ready to paint the content.
   SkRegion damaged_region_;
@@ skipping 47 matching lines @@
 
   // A cached copy of |Compositor::device_scale_factor()|.
   float device_scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_