scheduler: Throttle timers in out-of-view frames

components/scheduler/renderer/renderer_web_scheduler_impl.cc

Index: components/scheduler/renderer/renderer_web_scheduler_impl.cc
diff --git a/components/scheduler/renderer/renderer_web_scheduler_impl.cc b/components/scheduler/renderer/renderer_web_scheduler_impl.cc
index e53e01d3ca2320ffebd95348108bc52954f535d5..734d3fdde051c683f4666574e10b20be99df2a28 100644
--- a/components/scheduler/renderer/renderer_web_scheduler_impl.cc
+++ b/components/scheduler/renderer/renderer_web_scheduler_impl.cc
@@ -7,6 +7,7 @@
 #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"
@@ -14,6 +15,10 @@
 #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)
@@ -36,10 +41,16 @@ void RendererWebSchedulerImpl::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() {