CrOS: Set max frames pending for UI from command line.

content/renderer/gpu/compositor_output_surface.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/renderer/gpu/compositor_output_surface.h"
 
 #include "base/command_line.h"
 #include "base/message_loop_proxy.h"
 #include "cc/compositor_frame.h"
 #include "cc/compositor_frame_ack.h"
@@ skipping 47 matching lines @@
                     make_scoped_ptr(software_device)),
       output_surface_filter_(
           RenderThreadImpl::current()->compositor_output_surface_filter()),
       routing_id_(routing_id),
       prefers_smoothness_(false),
       main_thread_id_(base::PlatformThread::CurrentId()) {
   DCHECK(output_surface_filter_);
   CommandLine* command_line = CommandLine::ForCurrentProcess();
   capabilities_.has_parent_compositor = command_line->HasSwitch(
       switches::kEnableDelegatedRenderer);
+  if (capabilities_.has_parent_compositor)
+    capabilities_.max_frames_pending = 1;

[piman, 2013/03/13 15:55:22]

This logic should stay inside the compositor. It's necessary (at least
currently) for correctness of the DelegatingRenderer, so I'd rather not rely on
the embedder to do the right thing (which may change in the future).

[jonathan.backer, 2013/03/13 16:55:29]

Done.

   DetachFromThread();
 }
 
 CompositorOutputSurface::~CompositorOutputSurface() {
   DCHECK(CalledOnValidThread());
   if (!client_)
     return;
   UpdateSmoothnessTakesPriority(false);
   if (output_surface_proxy_)
     output_surface_proxy_->ClearOutputSurface();
@@ skipping 83 matching lines @@
   // If this is the last surface to stop preferring smoothness,
   // Reset the main thread's priority to the default.
   if (prefers_smoothness_ == true &&
       --g_prefer_smoothness_count == 0) {
     SetThreadsPriorityToDefault(main_thread_id_);
   }
   prefers_smoothness_ = prefers_smoothness;
 }
 
 }  // namespace content