scheduler: Throttle timers in out-of-view frames

components/scheduler/renderer/renderer_web_scheduler_impl.cc

 // Copyright 2015 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 "components/scheduler/renderer/renderer_web_scheduler_impl.h"
 
 #include <memory>
 
 #include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/memory/ptr_util.h"
 #include "components/scheduler/base/task_queue.h"
 #include "components/scheduler/common/scheduler_switches.h"
 #include "components/scheduler/renderer/renderer_scheduler_impl.h"
 #include "components/scheduler/renderer/web_view_scheduler_impl.h"
 
 namespace scheduler {
+namespace {
+const base::Feature kHiddenTimerThrottlingFeature{

[alex clarke (OOO till 29th), 2016/06/28 17:11:28]

nit: have you run git cl format?

[Sami, 2016/06/28 17:22:45]

Yep, looks like this is what it wants to do with initializers :P

+    "SchedulerHiddenTimerThrottling", base::FEATURE_ENABLED_BY_DEFAULT};
+}
 
 RendererWebSchedulerImpl::RendererWebSchedulerImpl(
     RendererSchedulerImpl* renderer_scheduler)
     : WebSchedulerImpl(renderer_scheduler,
                        renderer_scheduler->IdleTaskRunner(),
                        renderer_scheduler->LoadingTaskRunner(),
                        renderer_scheduler->TimerTaskRunner()),
       renderer_scheduler_(renderer_scheduler) {}
 
 RendererWebSchedulerImpl::~RendererWebSchedulerImpl() {
 }
 
 void RendererWebSchedulerImpl::suspendTimerQueue() {
   renderer_scheduler_->SuspendTimerQueue();
 }
 
 void RendererWebSchedulerImpl::resumeTimerQueue() {
   renderer_scheduler_->ResumeTimerQueue();
 }
 
 std::unique_ptr<blink::WebViewScheduler>
 RendererWebSchedulerImpl::createWebViewScheduler(blink::WebView* web_view) {
+  bool allow_hidden_timer_throttling = true;

[alex clarke (OOO till 29th), 2016/06/28 17:11:28]

Wait we're enabling this be default? Is that the right thing to do?

[Sami, 2016/06/28 17:22:45]

Yes, we're planning to use Finch to do a hold-out test, which is why I'm adding
a feature flag. I won't actually land this until I get 3xLGTM from my intent to
ship.

+  if (base::FeatureList::GetInstance()) {
+    allow_hidden_timer_throttling =
+        base::FeatureList::IsEnabled(kHiddenTimerThrottlingFeature);
+  }
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   return base::WrapUnique(new WebViewSchedulerImpl(
       web_view, renderer_scheduler_,
-      command_line->HasSwitch(switches::kDisableBackgroundTimerThrottling)));
+      command_line->HasSwitch(switches::kDisableBackgroundTimerThrottling),
+      allow_hidden_timer_throttling));
 }
 
 void RendererWebSchedulerImpl::onNavigationStarted() {
   renderer_scheduler_->OnNavigationStarted();
 }
 
 }  // namespace scheduler