scheduler: Add an unthrottled per-frame task runner

components/scheduler/renderer/renderer_scheduler.h

 // 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.
 
 #ifndef COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 #define COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 50 matching lines @@
   // TODO(alexclarke): Get rid of this default timer queue.
   virtual scoped_refptr<TaskQueue> TimerTaskRunner() = 0;
 
   // Returns a new loading task runner. This queue is intended for tasks related
   // to resource dispatch, foreground HTML parsing, etc...
   virtual scoped_refptr<TaskQueue> NewLoadingTaskRunner(const char* name) = 0;
 
   // Returns a new timer task runner. This queue is intended for DOM Timers.
   virtual scoped_refptr<TaskQueue> NewTimerTaskRunner(const char* name) = 0;
 
+  // Returns a task runner for tasks which should never get throttled.

[alex clarke (OOO till 29th), 2016/07/01 11:30:05]

Not necessarily for this patch, but I wonder if we should consider adding a
builder interface here, especially since we're thinking of supporting sub-task
queues and worklets (if those get traction).

[Sami, 2016/07/01 13:11:43]

That's a fine idea -- let's keep it in mind.

+  virtual scoped_refptr<TaskQueue> NewUnthrottledTaskRunner(
+      const char* name) = 0;
+
   // Returns a new RenderWidgetSchedulingState.  The signals from this will be
   // used to make scheduling decisions.
   virtual std::unique_ptr<RenderWidgetSchedulingState>
   NewRenderWidgetSchedulingState() = 0;
 
   // Called to notify about the start of an extended period where no frames
   // need to be drawn. Must be called from the main thread.
   virtual void BeginFrameNotExpectedSoon() = 0;
 
   // Called to notify about the start of a new frame.  Must be called from the
@@ skipping 94 matching lines @@
   virtual void SetRAILModeObserver(RAILModeObserver* observer) = 0;
 
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_