Do not give GPU memory to backgrounded compositors.

cc/output/gl_renderer.cc

 // 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.
 
 #include "cc/output/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 148 matching lines @@
                        ResourceProvider* resource_provider,
                        TextureMailboxDeleter* texture_mailbox_deleter,
                        int highp_threshold_min)
     : DirectRenderer(client, settings, output_surface, resource_provider),
       offscreen_framebuffer_id_(0),
       shared_geometry_quad_(gfx::RectF(-0.5f, -0.5f, 1.0f, 1.0f)),
       context_(output_surface->context_provider()->Context3d()),
       context_support_(output_surface->context_provider()->ContextSupport()),
       texture_mailbox_deleter_(texture_mailbox_deleter),
       is_backbuffer_discarded_(false),
-      discard_backbuffer_when_not_visible_(false),
       is_using_bind_uniform_(false),
       visible_(true),
       is_scissor_enabled_(false),
       stencil_shadow_(false),
       blend_shadow_(false),
       highp_threshold_min_(highp_threshold_min),
       highp_threshold_cache_(0),
       on_demand_tile_raster_resource_id_(0) {
   DCHECK(context_);
   DCHECK(context_support_);
@@ skipping 1916 matching lines @@
 
   // We don't have real fences, so we mark read fences as passed
   // assuming a double-buffered GPU pipeline. A texture can be
   // written to after one full frame has past since it was last read.
   if (last_swap_fence_.get())
     static_cast<SimpleSwapFence*>(last_swap_fence_.get())->SetHasPassed();
   last_swap_fence_ = resource_provider_->GetReadLockFence();
   resource_provider_->SetReadLockFence(new SimpleSwapFence());
 }
 
-void GLRenderer::SetDiscardBackBufferWhenNotVisible(bool discard) {
-  discard_backbuffer_when_not_visible_ = discard;
-  EnforceMemoryPolicy();
-}
-
 void GLRenderer::EnforceMemoryPolicy() {
   if (!visible_) {
     TRACE_EVENT0("cc", "GLRenderer::EnforceMemoryPolicy dropping resources");
     ReleaseRenderPassTextures();
-    if (discard_backbuffer_when_not_visible_)
-      DiscardBackbuffer();
+    DiscardBackbuffer();
     resource_provider_->ReleaseCachedData();
     GLC(context_, context_->flush());
   }
 }
 
 void GLRenderer::DiscardBackbuffer() {
   if (is_backbuffer_discarded_)
     return;
 
   output_surface_->DiscardBackbuffer();
@@ skipping 962 matching lines @@
   // The Skia GPU backend requires a stencil buffer.  See ReinitializeGrCanvas
   // implementation.
   return gr_context_ && context_->getContextAttributes().stencil;
 }
 
 bool GLRenderer::IsContextLost() {
   return (context_->getGraphicsResetStatusARB() != GL_NO_ERROR);
 }
 
 }  // namespace cc