cc: Allow sending BeginMainFrame before draw or activation

cc/scheduler/scheduler_settings.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/scheduler/scheduler_settings.h"
 
 namespace cc {
 
 SchedulerSettings::SchedulerSettings()
     : deadline_scheduling_enabled(true),
+      start_commit_before_draw_enabled(true),
+      start_commit_before_activate_enabled(false),

[Sami, 2014/02/18 18:45:50]

Should we dcheck in the scheduler constructor that
start_commit_before_activate_enabled implies start_commit_before_draw_enabled?
Just being paranoid :)

Also, maybe I missed it but should we have a test that explicitly turns on
start_commit_before_activate_enabled?

[brianderson, 2014/02/20 00:25:35]

A DCHECK sounds like a good idea.
I'll work on a scheduler unit test before landing. I'll probably avoid enabling
it in any of the layer tree tests until we might enable it by default.

       impl_side_painting(false),
       timeout_and_draw_when_animation_checkerboards(true),
       maximum_number_of_failed_draws_before_draw_is_forced_(3),
       using_synchronous_renderer_compositor(false),
       throttle_frame_production(true),
       switch_to_low_latency_if_possible(false) {}
 
 SchedulerSettings::~SchedulerSettings() {}
 
 }  // namespace cc