Remove GpuHostMsg_FrameDrawn and replace with client channel swap ack

content/common/gpu/client/command_buffer_proxy_impl.cc

Index: content/common/gpu/client/command_buffer_proxy_impl.cc
diff --git a/content/common/gpu/client/command_buffer_proxy_impl.cc b/content/common/gpu/client/command_buffer_proxy_impl.cc
index a0f67b3dedb55955c6cbb71f0bea71a06cc660b0..9f3497c41e4d37afe59cf2135fd5b89b30ece133 100644
--- a/content/common/gpu/client/command_buffer_proxy_impl.cc
+++ b/content/common/gpu/client/command_buffer_proxy_impl.cc
@@ -47,6 +47,8 @@ bool CommandBufferProxyImpl::OnMessageReceived(const IPC::Message& message) {
                         OnSetMemoryAllocation);
     IPC_MESSAGE_HANDLER(GpuCommandBufferMsg_SignalSyncPointAck,
                         OnSignalSyncPointAck);
+    IPC_MESSAGE_HANDLER(GpuCommandBufferMsg_SwapBuffersCompleted,
+                        OnSwapBuffersCompleted);
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
@@ -187,7 +189,9 @@ void CommandBufferProxyImpl::Flush(int32 put_offset) {
 }
 
 void CommandBufferProxyImpl::SetLatencyInfo(
-    const std::vector<ui::LatencyInfo>& latency_info) {
+    const std::vector<ui::LatencyInfo>& latency_info,
+    const SwapBuffersCompletionCallback& callback) {
+  swap_buffers_completion_callback_ = callback;
   for (size_t i = 0; i < latency_info.size(); i++)
     latency_info_.push_back(latency_info[i]);
 }
@@ -504,4 +508,12 @@ gpu::CommandBufferSharedState* CommandBufferProxyImpl::shared_state() const {
       shared_state_shm_->memory());
 }
 
+void CommandBufferProxyImpl::OnSwapBuffersCompleted(
+    const std::vector<ui::LatencyInfo>& latency_info) {

[Mike West, 2014/10/07 04:46:23]

It doesn't look like you have any limits on the amount of data that can be sent
back and forth over this message. It seems like calling LatencyInfo::Verify on
this vector would be a reasonable way of enforcing sanity checks. WDYT?

+  if (!swap_buffers_completion_callback_.is_null()) {
+    swap_buffers_completion_callback_.Run(latency_info);
+    swap_buffers_completion_callback_.Reset();

[piman, 2014/10/07 02:30:39]

If we have more than 1 frame deep, I don't think this will work, because we may
call a second SetLatencyInfo+SwapBuffers before we got the first ack, and so the
second callback will never fire.

[no sievers, 2014/10/07 19:47:24]

Done.

+  }
+}
+
 }  // namespace content