cc: Use HighResNow as timebase if it is fast and reliable

cc/trees/single_thread_proxy.cc

 // Copyright 2011 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/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "cc/debug/benchmark_instrumentation.h"
 #include "cc/output/context_provider.h"
 #include "cc/output/output_surface.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/resources/prioritized_resource_manager.h"
 #include "cc/resources/resource_update_controller.h"
 #include "cc/trees/blocking_task_runner.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
+#include "ui/gfx/frame_time.h"
 
 namespace cc {
 
 scoped_ptr<Proxy> SingleThreadProxy::Create(LayerTreeHost* layer_tree_host) {
   return make_scoped_ptr(
       new SingleThreadProxy(layer_tree_host)).PassAs<Proxy>();
 }
 
 SingleThreadProxy::SingleThreadProxy(LayerTreeHost* layer_tree_host)
     : Proxy(NULL),
@@ skipping 24 matching lines @@
   DCHECK(!layer_tree_host_impl_);
 }
 
 bool SingleThreadProxy::CompositeAndReadback(void* pixels, gfx::Rect rect) {
   TRACE_EVENT0("cc", "SingleThreadProxy::CompositeAndReadback");
   DCHECK(Proxy::IsMainThread());
 
   gfx::Rect device_viewport_damage_rect = rect;
 
   LayerTreeHostImpl::FrameData frame;
-  if (!CommitAndComposite(base::TimeTicks::Now(),
+  if (!CommitAndComposite(gfx::FrameTime::Now(),

[ajuma, 2013/10/17 20:14:56]

We'll also need to fix the other call to CommitAndComposite (from
CompositeImmediately below), which means tracing back to where the time passed
in to CommitAndComposite comes from. I believe RenderWidget::DoDeferredUpdate
and ui::Compositor::Draw are two such places. Also, looking at ui::Compositor,
SchedulerDraw() calls LayerTreeHost::Composite with a TimeTicks::Now().

                           device_viewport_damage_rect,
                           true,  // for_readback
                           &frame))
     return false;
 
   {
     DebugScopedSetImplThread impl(this);
     layer_tree_host_impl_->Readback(pixels, rect);
 
     if (layer_tree_host_impl_->IsContextLost())
@@ skipping 456 matching lines @@
 void SingleThreadProxy::DidSwapFrame() {
   if (next_frame_is_newly_committed_frame_) {
     next_frame_is_newly_committed_frame_ = false;
     layer_tree_host_->DidCommitAndDrawFrame();
   }
 }
 
 bool SingleThreadProxy::CommitPendingForTesting() { return false; }
 
 }  // namespace cc