Fix Omnibox.CharTypedToRepaintLatency regression with D3DVsync experiment

content/browser/compositor/gpu_vsync_begin_frame_source.cc

Index: content/browser/compositor/gpu_vsync_begin_frame_source.cc
diff --git a/content/browser/compositor/gpu_vsync_begin_frame_source.cc b/content/browser/compositor/gpu_vsync_begin_frame_source.cc
index 7e43be479adc6b1ff83bc7337b8cf60b29b15855..e4f039a782e5d99eb0121fd177d3b9d23dc6ffcb 100644
--- a/content/browser/compositor/gpu_vsync_begin_frame_source.cc
+++ b/content/browser/compositor/gpu_vsync_begin_frame_source.cc
@@ -22,7 +22,7 @@ void GpuVSyncBeginFrameSource::OnVSync(base::TimeTicks timestamp,
   if (!needs_begin_frames_)
     return;
 
-  base::TimeTicks now = base::TimeTicks::Now();
+  base::TimeTicks now = Now();
   base::TimeTicks deadline = now.SnappedToNextTick(timestamp, interval);
 
   TRACE_EVENT1("cc", "GpuVSyncBeginFrameSource::OnVSync", "latency",
@@ -39,4 +39,43 @@ void GpuVSyncBeginFrameSource::OnNeedsBeginFrames(bool needs_begin_frames) {
   vsync_control_->SetNeedsVSync(needs_begin_frames);
 }
 
+base::TimeTicks GpuVSyncBeginFrameSource::Now() const {
+  return base::TimeTicks::Now();
+}
+
+cc::BeginFrameArgs GpuVSyncBeginFrameSource::GetMissedBeginFrameArgs(
+    cc::BeginFrameObserver* obs) {
+  if (!last_begin_frame_args_.IsValid())
+    return cc::BeginFrameArgs();
+
+  base::TimeTicks now = Now();
+  base::TimeTicks estimated_next_timestamp = now.SnappedToNextTick(
+      last_begin_frame_args_.frame_time, last_begin_frame_args_.interval);
+  base::TimeTicks missed_timestamp =
+      estimated_next_timestamp - last_begin_frame_args_.interval;
+
+  if (missed_timestamp > last_begin_frame_args_.frame_time) {
+    // The projected missed timestamp is newer than the last known timestamp.
+    // In this case create BeginFrameArgs with a new sequence number.
+    next_sequence_number_++;
+    last_begin_frame_args_ = cc::BeginFrameArgs::Create(
+        BEGINFRAME_FROM_HERE, source_id(), next_sequence_number_,
+        missed_timestamp, estimated_next_timestamp,
+        last_begin_frame_args_.interval, cc::BeginFrameArgs::MISSED);
+    return last_begin_frame_args_;
+  }
+
+  // The last known args object is up-to-date. Skip sending notification
+  // if the observer has already seen it.
+  const cc::BeginFrameArgs& last_observer_args = obs->LastUsedBeginFrameArgs();
+  if (last_observer_args.IsValid() &&
+      last_begin_frame_args_.frame_time <= last_observer_args.frame_time) {
+    return cc::BeginFrameArgs();
+  }
+
+  cc::BeginFrameArgs missed_args = last_begin_frame_args_;
+  missed_args.type = cc::BeginFrameArgs::MISSED;
+  return missed_args;
+}
+
 }  // namespace content