Aggressively discard tiles on OS X to see if it improves

content/common/gpu/gpu_memory_manager.cc

 // Copyright (c) 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.
 
 #include "content/common/gpu/gpu_memory_manager.h"
 
 #if defined(ENABLE_GPU)
 
 #include <algorithm>
 
@@ skipping 465 matching lines @@
        ++it) {
     ClientState* client_state = *it;
     GpuMemoryAllocation allocation;
     if (client_state->has_surface) {
       allocation.browser_allocation.suggest_have_frontbuffer =
           !client_state->hibernated;
 
       // Set the state when visible.
       allocation.renderer_allocation.bytes_limit_when_visible =
           bytes_limit_when_visible;
+      // Experiment to determine if aggressively discarding tiles on OS X
+      // results in greater stability.
+#if defined(OS_MACOSX)
+      allocation.renderer_allocation.priority_cutoff_when_visible =
+          GpuMemoryAllocationForRenderer::kPriorityCutoffAllowNiceToHave;
+#else
       allocation.renderer_allocation.priority_cutoff_when_visible =
           GpuMemoryAllocationForRenderer::kPriorityCutoffAllowEverything;
+#endif
 
       // Set the state when backgrounded.
       bool allow_allocation_when_backgrounded = false;
       if (client_state->visible) {
         // If the client is visible, then allow it to keep its textures, should
         // it be backgrounded, but only if all textures required to draw will
         // fit in total backgrounded memory limit.
         allow_allocation_when_backgrounded =
             client_state->managed_memory_stats.bytes_required <
             bytes_backgrounded_available_gpu_memory_;
@@ skipping 131 matching lines @@
     : client(client),
       has_surface(has_surface),
       visible(visible),
       last_used_time(last_used_time),
       hibernated(false) {
 }
 
 }  // namespace content
 
 #endif