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 69 matching lines @@
 
 using blink::WebFloatPoint;
 using blink::WebRect;
 using blink::WebSelection;
 using blink::WebSize;
 using blink::WebBrowserControlsState;
 
 namespace content {
 namespace {
 
+using ReportTimeCallback = base::Callback<void(bool, double)>;
+
+double MonotonicallyIncreasingTime() {
+  return static_cast<double>(base::TimeTicks::Now().ToInternalValue()) /
+         base::Time::kMicrosecondsPerSecond;
+}
+
+class ReportTimeSwapPromise : public cc::SwapPromise {
+ public:
+  ReportTimeSwapPromise(
+      ReportTimeCallback callback,
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
+  ~ReportTimeSwapPromise() override;
+
+  void DidActivate() override {}
+  void WillSwap(cc::CompositorFrameMetadata* metadata) override {}
+  void DidSwap() override;
+  DidNotSwapAction DidNotSwap(DidNotSwapReason reason) override;
+
+  int64_t TraceId() const override;
+
+ private:
+  ReportTimeCallback callback_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReportTimeSwapPromise);
+};
+
+ReportTimeSwapPromise::ReportTimeSwapPromise(
+    ReportTimeCallback callback,
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
+    : callback_(callback), task_runner_(task_runner) {}
+
+ReportTimeSwapPromise::~ReportTimeSwapPromise() {}
+
+void ReportTimeSwapPromise::DidSwap() {
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::BindOnce(callback_, true, MonotonicallyIncreasingTime()));
+}
+
+cc::SwapPromise::DidNotSwapAction ReportTimeSwapPromise::DidNotSwap(
+    cc::SwapPromise::DidNotSwapReason reason) {
+  task_runner_->PostTask(FROM_HERE, base::BindOnce(callback_, false, 0));
+  return cc::SwapPromise::DidNotSwapAction::BREAK_PROMISE;
+}
+
+int64_t ReportTimeSwapPromise::TraceId() const {
+  return 0;
+}
+
 bool GetSwitchValueAsInt(const base::CommandLine& command_line,
                          const std::string& switch_string,
                          int min_value,
                          int max_value,
                          int* result) {
   std::string string_value = command_line.GetSwitchValueASCII(switch_string);
   int int_value;
   if (base::StringToInt(string_value, &int_value) && int_value >= min_value &&
       int_value <= max_value) {
     *result = int_value;
@@ skipping 1048 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(ReportTimeCallback callback) {
+  QueueSwapPromise(base::MakeUnique<ReportTimeSwapPromise>(
+      std::move(callback), base::ThreadTaskRunnerHandle::Get()));
+}
+
 }  // namespace content