Plumbing input event latency reporting through Mus GPU.

gpu/ipc/in_process_command_buffer.cc

Index: gpu/ipc/in_process_command_buffer.cc
diff --git a/gpu/ipc/in_process_command_buffer.cc b/gpu/ipc/in_process_command_buffer.cc
index fe7d2fa998ce6b274f30795f76109fc6bf514f92..3e4673bb6dfd646794e352e0e0f52a382de82198 100644
--- a/gpu/ipc/in_process_command_buffer.cc
+++ b/gpu/ipc/in_process_command_buffer.cc
@@ -558,6 +558,13 @@ void InProcessCommandBuffer::FlushOnGpuThread(int32_t put_offset) {
   ScopedEvent handle_flush(&flush_event_);
   base::AutoLock lock(command_buffer_lock_);
 
+  if (ui::LatencyInfo::Verify(latency_info_,

[piman, 2017/04/10 23:50:34]

latency_info_ is written on another thread (without lock), so it's unsafe to
read (or modify) here.

I think what should happen instead is that InProcessCommandBuffer::Flush should
extract the latency_info_ and pass it to the queued task (i.e. bound to this
function).

[mfomitchev, 2017/04/13 03:00:00]

Done.

+                              "InProcessCommandBuffer::FlushOnGpuThread") &&
+      !latency_info_callback_.is_null()) {
+    latency_info_callback_.Run(latency_info_);
+  }
+  latency_info_.clear();
+
   command_buffer_->Flush(put_offset);
   // Update state before signaling the flush event.
   UpdateLastStateOnGpuThread();
@@ -991,6 +998,12 @@ bool InProcessCommandBuffer::CanWaitUnverifiedSyncToken(
   return sync_token.namespace_id() == GetNamespaceID();
 }
 
+void InProcessCommandBuffer::AddLatencyInfo(
+    const std::vector<ui::LatencyInfo>& latency_info) {
+  latency_info_.insert(latency_info_.end(), latency_info.begin(),
+                       latency_info.end());
+}
+
 #if defined(OS_WIN)
 void InProcessCommandBuffer::DidCreateAcceleratedSurfaceChildWindow(
     SurfaceHandle parent_window,
@@ -1017,7 +1030,7 @@ const gles2::FeatureInfo* InProcessCommandBuffer::GetFeatureInfo() const {
 
 void InProcessCommandBuffer::SetLatencyInfoCallback(
     const LatencyInfoCallback& callback) {
-  // TODO(fsamuel): Implement this.
+  latency_info_callback_ = callback;
 }
 
 void InProcessCommandBuffer::UpdateVSyncParameters(base::TimeTicks timebase,