Do not give GPU memory to backgrounded compositors.

cc/output/gl_renderer.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_OUTPUT_GL_RENDERER_H_
 #define CC_OUTPUT_GL_RENDERER_H_
 
 #include "base/cancelable_callback.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
@@ skipping 55 matching lines @@
   virtual void GetFramebufferPixels(void* pixels, gfx::Rect rect) OVERRIDE;
 
   virtual bool IsContextLost() OVERRIDE;
 
   virtual void SetVisible(bool visible) OVERRIDE;
 
   virtual void SendManagedMemoryStats(size_t bytes_visible,
                                       size_t bytes_visible_and_nearby,
                                       size_t bytes_allocated) OVERRIDE;
 
-  virtual void SetDiscardBackBufferWhenNotVisible(bool discard) OVERRIDE;
-
   static void DebugGLCall(WebKit::WebGraphicsContext3D* context,
                           const char* command,
                           const char* file,
                           int line);
 
   bool CanUseSkiaGPUBackend() const;
 
  protected:
   GLRenderer(RendererClient* client,
              const LayerTreeSettings* settings,
@@ skipping 343 matching lines @@
 
   skia::RefPtr<GrContext> gr_context_;
   skia::RefPtr<SkCanvas> sk_canvas_;
 
   TextureMailboxDeleter* texture_mailbox_deleter_;
 
   gfx::Rect swap_buffer_rect_;
   gfx::Rect scissor_rect_;
   gfx::Rect viewport_;
   bool is_backbuffer_discarded_;
-  bool discard_backbuffer_when_not_visible_;
   bool is_using_bind_uniform_;
   bool visible_;
   bool is_scissor_enabled_;
   bool stencil_shadow_;
   bool blend_shadow_;
   unsigned program_shadow_;
   TexturedQuadDrawCache draw_cache_;
   int highp_threshold_min_;
   int highp_threshold_cache_;
 
@@ skipping 18 matching lines @@
 #if DEBUG_GL_CALLS && !defined(NDEBUG)
 #define GLC(context, x)                                                        \
   (x, GLRenderer::DebugGLCall(&* context, #x, __FILE__, __LINE__))
 #else
 #define GLC(context, x) (x)
 #endif
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_GL_RENDERER_H_