Enable disabling WebCore::GraphicsContext in telemetry.

cc/layers/content_layer_client.h

 // Copyright 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 CC_LAYERS_CONTENT_LAYER_CLIENT_H_
 #define CC_LAYERS_CONTENT_LAYER_CLIENT_H_
 
 #include "cc/base/cc_export.h"
 
 class SkCanvas;
 
 namespace gfx {
 class Rect;
 class RectF;
 }
 
 namespace cc {
 
 class CC_EXPORT ContentLayerClient {
  public:
-  virtual void PaintContents(SkCanvas* canvas,
-                             const gfx::Rect& clip,
-                             gfx::RectF* opaque) = 0;
+  enum GraphicsContextStatus {
+    GraphicsContextEnabled,

[Sami, 2014/05/01 16:32:53]

nit: Swap the order of these two so that enabled = 1?

[danakj, 2014/05/01 17:07:11]

+1

[Stephen Chennney, 2014/05/01 19:12:26]

Done.
And also switched to Chromium style for enums.

+    GraphicsContextDisabled
+  };
+
+  virtual void PaintContents(
+      SkCanvas* canvas,
+      const gfx::Rect& clip,
+      gfx::RectF* opaque,
+      GraphicsContextStatus
+          graphics_context_state = GraphicsContextEnabled) = 0;

[Sami, 2014/05/01 16:32:53]

Chromium style prohibits default parameters, but it looks like this is always
passed in so we could just make it required?

[Stephen Chennney, 2014/05/01 19:12:26]

Done.

Means changing more files, but that's life.

 
   // Called by the content layer during the update phase.
   // If the client paints LCD text, it may want to invalidate the layer.
   virtual void DidChangeLayerCanUseLCDText() = 0;
 
   // If true the layer may skip clearing the background before rasterizing,
   // because it will cover any uncleared data with content.
   virtual bool FillsBoundsCompletely() const = 0;
 
  protected:
   virtual ~ContentLayerClient() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_CONTENT_LAYER_CLIENT_H_