Force events to be non blocking if main thread is unresponsive.

third_party/WebKit/public/platform/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 THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 #define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 168 matching lines @@
   virtual void SetTopLevelBlameContext(
       base::trace_event::BlameContext* blame_context) = 0;
 
   // The renderer scheduler maintains an estimated RAIL mode[1]. This observer
   // can be used to get notified when the mode changes. The observer will be
   // called on the main thread and must outlive this class.
   // [1]
   // https://developers.google.com/web/tools/chrome-devtools/profile/evaluate-performance/rail
   virtual void SetRAILModeObserver(RAILModeObserver* observer) = 0;
 
+  // Returns whether or not the main thread appears unresponsive, based on the
+  // length and frequency of recent main thread tasks.
+  virtual bool MainThreadSeemsUnresponsive() const = 0;
+
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_