Use swap-promise to improve first* paint times

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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/renderer/gpu/render_widget_compositor.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 23 matching lines @@
 #include "cc/base/switches.h"
 #include "cc/benchmarks/micro_benchmark.h"
 #include "cc/blink/web_layer_impl.h"
 #include "cc/debug/layer_tree_debug_state.h"
 #include "cc/input/layer_selection_bound.h"
 #include "cc/layers/layer.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "cc/output/latency_info_swap_promise.h"
+#include "cc/output/report_time_swap_promise.h"
 #include "cc/output/swap_promise.h"
 #include "cc/resources/single_release_callback.h"
 #include "cc/scheduler/begin_frame_source.h"
 #include "cc/trees/latency_info_swap_promise_monitor.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_mutator.h"
 #include "content/common/content_switches_internal.h"
 #include "content/common/layer_tree_settings_factory.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
@@ skipping 1094 matching lines @@
 
 void RenderWidgetCompositor::SetContentSourceId(uint32_t id) {
   layer_tree_host_->SetContentSourceId(id);
 }
 
 void RenderWidgetCompositor::SetLocalSurfaceId(
     const cc::LocalSurfaceId& local_surface_id) {
   layer_tree_host_->SetLocalSurfaceId(local_surface_id);
 }
 
+void RenderWidgetCompositor::NotifySwapTime(
+    base::Callback<void(bool, double)> callback) {
+  QueueSwapPromise(base::MakeUnique<cc::ReportTimeSwapPromise>(

[enne (OOO), 2017/05/01 21:58:11]

Agreed with sunnyps that ReportSwapTimePromise could just live in
render_widget_compositor.cc.

[panicker, 2017/05/02 00:57:04]

Done.

+      std::move(callback), base::ThreadTaskRunnerHandle::Get()));
+}
+
 }  // namespace content