Route D3D VSync signal to Compositor

content/browser/compositor/gpu_vsync_begin_frame_source.cc

+// Copyright 2016 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/browser/compositor/gpu_vsync_begin_frame_source.h"
+
+namespace content {
+
+GpuVSyncBeginFrameSource::GpuVSyncBeginFrameSource(
+    GpuVSyncControl* vsync_control)
+    : cc::ExternalBeginFrameSource(this),
+      vsync_control_(vsync_control),
+      needs_begin_frames_(false),
+      next_sequence_number_(cc::BeginFrameArgs::kStartingFrameNumber) {
+  DCHECK(vsync_control);
+}
+
+GpuVSyncBeginFrameSource::~GpuVSyncBeginFrameSource() = default;
+
+void GpuVSyncBeginFrameSource::OnVSync(
+    base::TimeTicks timestamp, base::TimeDelta interval) {
+  if (!needs_begin_frames_)
+    return;
+
+  base::TimeTicks now = base::TimeTicks::Now();
+  base::TimeTicks deadline = now.SnappedToNextTick(timestamp, interval);
+
+  TRACE_EVENT1("cc", "GpuVSyncBeginFrameSource::OnVSync",
+               "latency", (now - timestamp).ToInternalValue());
+
+  next_sequence_number_++;

[sunnyps, 2017/01/25 01:36:41]

I think you want to increment seq num after begin frame.

+  OnBeginFrame(cc::BeginFrameArgs::Create(
+      BEGINFRAME_FROM_HERE, source_id(), next_sequence_number_, timestamp,
+      deadline, interval, cc::BeginFrameArgs::NORMAL));
+}
+
+void GpuVSyncBeginFrameSource::OnNeedsBeginFrames(bool needs_begin_frames) {
+  needs_begin_frames_ = needs_begin_frames;
+  vsync_control_->SetNeedsVSync(needs_begin_frames);
+}
+
+}  // namespace content