content: Implement dynamic priorities for raster threads.

cc/raster/task_graph_runner.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 CC_RASTER_TASK_GRAPH_RUNNER_H_
 #define CC_RASTER_TASK_GRAPH_RUNNER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 19 matching lines @@
 
   // Subclasses should implement this method. RunOnWorkerThread may be called
   // on any thread, and subclasses are responsible for locking and thread
   // safety.
   virtual void RunOnWorkerThread() = 0;
 
   void WillRun();
   void DidRun();
   bool HasFinishedRunning() const;
 
+  bool cancelled;
+
  protected:
   friend class base::RefCountedThreadSafe<Task>;
 
   Task();
   virtual ~Task();
 
   bool will_run_;
   bool did_run_;
 };
 
@@ skipping 167 matching lines @@
  private:
   TaskGraph* graph_;
   const Task* task_;
   size_t current_index_;
   TaskGraph::Node* current_node_;
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_TASK_GRAPH_RUNNER_H_