time metric: record elapsed time from when the backgrounded and purged renderer is foregrounded unti

content/renderer/render_widget.cc

 // Copyright (c) 2012 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/render_widget.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 357 matching lines @@
       popup_origin_scale_for_emulation_(0.f),
       frame_swap_message_queue_(new FrameSwapMessageQueue()),
       resizing_mode_selector_(new ResizingModeSelector()),
       has_host_context_menu_location_(false),
       has_added_input_handler_(false),
       has_focus_(false),
 #if defined(OS_MACOSX)
       text_input_client_observer_(new TextInputClientObserver(this)),
 #endif
       focused_pepper_plugin_(nullptr),
+      time_to_first_active_paint_recorded_(true),
+      was_shown_time_(base::TimeTicks::Now()),
       weak_ptr_factory_(this) {
   DCHECK_NE(routing_id_, MSG_ROUTING_NONE);
   if (!swapped_out)
     RenderProcess::current()->AddRefProcess();
   DCHECK(RenderThread::Get());
 
   // In tests there may not be a RenderThreadImpl.
   if (RenderThreadImpl::current()) {
     render_widget_scheduling_state_ = RenderThreadImpl::current()
                                           ->GetRendererScheduler()
@@ skipping 378 matching lines @@
     observer.WasHidden();
 }
 
 void RenderWidget::OnWasShown(bool needs_repainting,
                               const ui::LatencyInfo& latency_info) {
   TRACE_EVENT0("renderer", "RenderWidget::OnWasShown");
   // During shutdown we can just ignore this message.
   if (!GetWebWidget())
     return;
 
+  was_shown_time_ = base::TimeTicks::Now();
   // See OnWasHidden
   SetHidden(false);
   for (auto& observer : render_frames_)
     observer.WasShown();
 
   if (!needs_repainting)
     return;
 
   // Generate a full repaint.
   if (compositor_) {
@@ skipping 136 matching lines @@
 bool RenderWidget::IsClosing() const {
   return host_closing_;
 }
 
 void RenderWidget::RequestScheduleAnimation() {
   scheduleAnimation();
 }
 
 void RenderWidget::UpdateVisualState() {
   GetWebWidget()->updateAllLifecyclePhases();
+
+  RenderThreadImpl* render_thread_impl = RenderThreadImpl::current();
+  if (!time_to_first_active_paint_recorded_ &&

[esprehn, 2017/02/08 06:23:06]

You want to do the time_to_first_active_paint_recorded_ first, and then do
RenderThreadImpl::current() inside a block. Otherwise we're doing the extra TLS
lookup every time even though we early out at the bool.

if (time_to_first_active_paint_recorded_)
  return;
RenderThreadImpl* thread_impl = RenderThreadImpl::current();
...

[tasak, 2017/02/08 06:49:07]

Done.

+      render_thread_impl->NeedsToRecordFirstActivePaint()) {
+    time_to_first_active_paint_recorded_ = true;
+    base::TimeDelta sample = base::TimeTicks::Now() - was_shown_time_;
+    UMA_HISTOGRAM_TIMES("PurgeAndSuspend.Experimental.TimeToFirstActivePaint",
+                        sample);
+  }
 }
 
 void RenderWidget::WillBeginCompositorFrame() {
   TRACE_EVENT0("gpu", "RenderWidget::willBeginCompositorFrame");
 
   // The UpdateTextInputState can result in further layout and possibly
   // enable GPU acceleration so they need to be called before any painting
   // is done.
   UpdateTextInputState();
   UpdateSelectionBounds();
@@ skipping 933 matching lines @@
 }
 
 void RenderWidget::SetHidden(bool hidden) {
   if (is_hidden_ == hidden)
     return;
 
   // The status has changed.  Tell the RenderThread about it and ensure
   // throttled acks are released in case frame production ceases.
   is_hidden_ = hidden;
 
-  if (is_hidden_)
+  if (is_hidden_) {
     RenderThreadImpl::current()->WidgetHidden();
-  else
+    time_to_first_active_paint_recorded_ = false;
+  } else
     RenderThreadImpl::current()->WidgetRestored();
 
   if (render_widget_scheduling_state_)
     render_widget_scheduling_state_->SetHidden(hidden);
 }
 
 void RenderWidget::DidToggleFullscreen() {
   if (!GetWebWidget())
     return;
 
@@ skipping 395 matching lines @@
     // browser side (https://crbug.com/669219).
     // If there is no WebFrameWidget, then there will be no
     // InputMethodControllers for a WebLocalFrame.
     return nullptr;
   }
   return static_cast<blink::WebFrameWidget*>(GetWebWidget())
       ->getActiveWebInputMethodController();
 }
 
 }  // namespace content