Do not give GPU memory to backgrounded compositors.

cc/trees/layer_tree_host_pixeltest_on_demand_raster.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/layers/append_quads_data.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_layer.h"
 #include "cc/layers/picture_layer_impl.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/test/layer_tree_pixel_test.h"
@@ skipping 12 matching lines @@
 class LayerTreeHostOnDemandRasterPixelTest : public LayerTreePixelTest {
  public:
   virtual void InitializeSettings(LayerTreeSettings* settings) OVERRIDE {
     settings->impl_side_painting = true;
   }
 
   virtual void BeginCommitOnThread(LayerTreeHostImpl* impl) OVERRIDE {
     // Not enough memory available. Enforce on-demand rasterization.
     impl->SetMemoryPolicy(
         ManagedMemoryPolicy(1, gpu::MemoryAllocation::CUTOFF_ALLOW_EVERYTHING,
-                            1, gpu::MemoryAllocation::CUTOFF_ALLOW_NOTHING,
                             1000));
-    impl->SetDiscardBackBufferWhenNotVisible(true);
   }
 
   virtual void SwapBuffersOnThread(LayerTreeHostImpl* host_impl,
                                    bool result) OVERRIDE {
     // Find the PictureLayerImpl ask it to append quads to check their material.
     // The PictureLayerImpl is assumed to be the first child of the root layer
     // in the active tree.
     PictureLayerImpl* picture_layer = static_cast<PictureLayerImpl*>(
         host_impl->active_tree()->root_layer()->child_at(0));
 
@@ skipping 57 matching lines @@
 
   RunPixelTest(GL_WITH_BITMAP,
                layer,
                base::FilePath(FILE_PATH_LITERAL("blue_yellow.png")));
 }
 
 }  // namespace
 }  // namespace cc
 
 #endif  // OS_ANDROID