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

cc/layer.h

 // Copyright 2010 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 CC_LAYER_H_
 #define CC_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 181 matching lines @@
     void setUseParentBackfaceVisibility(bool useParentBackfaceVisibility) { m_useParentBackfaceVisibility = useParentBackfaceVisibility; }
     bool useParentBackfaceVisibility() const { return m_useParentBackfaceVisibility; }
 
     virtual void setLayerTreeHost(LayerTreeHost*);
 
     bool hasDelegatedContent() const { return false; }
     bool hasContributingDelegatedRenderPasses() const { return false; }
 
     void setIsDrawable(bool);
 
+    void setVisible(bool);

[piman, 2013/01/30 21:38:50]

Nit: we may want to name that as "setSubtreeVisible" or something that carries
the fact that this applies to this layer and its entire subtree, not just this
layer.

+    bool visible() const { return m_visible; }
+
     void setReplicaLayer(Layer*);
     Layer* replicaLayer() { return m_replicaLayer.get(); }
     const Layer* replicaLayer() const { return m_replicaLayer.get(); }
 
     bool hasMask() const { return !!m_maskLayer; }
     bool hasReplica() const { return !!m_replicaLayer; }
     bool replicaHasMask() const { return m_replicaLayer && (m_maskLayer || m_replicaLayer->m_maskLayer); }
 
     // These methods typically need to be overwritten by derived classes.
     virtual bool drawsContent() const;
@@ skipping 160 matching lines @@
     SkColor m_backgroundColor;
     std::string m_debugName;
     float m_opacity;
     skia::RefPtr<SkImageFilter> m_filter;
     WebKit::WebFilterOperations m_filters;
     WebKit::WebFilterOperations m_backgroundFilters;
     float m_anchorPointZ;
     bool m_isContainerForFixedPositionLayers;
     bool m_fixedToContainerLayer;
     bool m_isDrawable;
+    bool m_visible;
     bool m_masksToBounds;
     bool m_contentsOpaque;
     bool m_doubleSided;
     bool m_preserves3D;
     bool m_useParentBackfaceVisibility;
     bool m_drawCheckerboardForMissingTiles;
     bool m_forceRenderSurface;
 
     gfx::Transform m_transform;
     gfx::Transform m_sublayerTransform;
@@ skipping 12 matching lines @@
     WebKit::WebLayerScrollClient* m_layerScrollClient;
 
     DrawProperties<Layer, RenderSurface> m_drawProperties;
 };
 
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*);
 
 }  // namespace cc
 
 #endif  // CC_LAYER_H_