Experimental 'purging and suspending' backgrounded tabs behind the flag

components/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 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_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 369 matching lines @@
                "RendererSchedulerImpl::OnRendererForegrounded");
   helper_.CheckOnValidThread();
   if (helper_.IsShutdown() || !MainThreadOnly().renderer_backgrounded)
     return;
 
   MainThreadOnly().renderer_backgrounded = false;
   suspend_timers_when_backgrounded_closure_.Cancel();
   ResumeTimerQueueWhenForegrounded();
 }
 
+void RendererSchedulerImpl::SuspendRenderer() {
+  helper_.CheckOnValidThread();
+  DCHECK(MainThreadOnly().renderer_backgrounded);
+  if (helper_.IsShutdown())
+    return;
+  suspend_timers_when_backgrounded_closure_.Cancel();

[Sami, 2016/05/12 11:31:35]

Could you add a TODO about possibly suspending other types of tasks too (e.g.,
loading tasks)?

[hajimehoshi, 2016/05/13 06:07:45]

Done.

+  SuspendTimerQueueWhenBackgrounded();
+}
+
 void RendererSchedulerImpl::EndIdlePeriod() {
   if (MainThreadOnly().in_idle_period_for_testing)
     return;
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
                "RendererSchedulerImpl::EndIdlePeriod");
   helper_.CheckOnValidThread();
   idle_helper_.EndIdlePeriod();
 }
 
 void RendererSchedulerImpl::EndIdlePeriodForTesting(
@@ skipping 860 matching lines @@
     }
     MainThreadOnly().have_reported_blocking_intervention_since_navigation =
         true;
     BroadcastConsoleWarning(
         "Deferred long-running timer task(s) to improve scrolling smoothness. "
         "See crbug.com/574343.");
   }
 }
 
 }  // namespace scheduler