Do not give GPU memory to backgrounded compositors.

cc/test/pixel_test.cc

 // Copyright 2013 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.
 
 #include "cc/test/pixel_test.h"
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "cc/base/switches.h"
@@ skipping 46 matching lines @@
   virtual void DidLoseOutputSurface() OVERRIDE {}
   virtual void SetExternalDrawConstraints(
       const gfx::Transform& transform,
       gfx::Rect viewport,
       gfx::Rect clip,
       bool valid_for_tile_management) OVERRIDE {
     device_viewport_ = viewport;
     device_clip_ = clip;
   }
   virtual void SetMemoryPolicy(const ManagedMemoryPolicy& policy) OVERRIDE {}
-  virtual void SetDiscardBackBufferWhenNotVisible(bool discard) OVERRIDE {}
   virtual void SetTreeActivationCallback(const base::Closure&) OVERRIDE {}
 
  private:
   gfx::Rect device_viewport_;
   gfx::Rect device_clip_;
 };
 
 PixelTest::PixelTest()
     : device_viewport_size_(gfx::Size(200, 200)),
       disable_picture_quad_image_filtering_(false),
@@ skipping 135 matching lines @@
   resource_provider_ =
       ResourceProvider::Create(output_surface_.get(), NULL, 0, false);
   renderer_ = SoftwareRenderer::Create(fake_client_.get(),
                                        &settings_,
                                        output_surface_.get(),
                                        resource_provider_.get())
       .PassAs<DirectRenderer>();
 }
 
 }  // namespace cc