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>
 
 #include <algorithm>
 #include <map>
 #include <vector>
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/threading/simple_thread.h"
+#include "base/time/time.h"
 #include "cc/base/cc_export.h"
+#include "cc/raster/task_category.h"
 
 namespace cc {
 
 class TaskGraphRunner;
 
+class CC_EXPORT TaskWorker {
+ public:
+  // TODO(prashant.n): Find better names.
+  virtual bool TaskSpeedup() = 0;
+  virtual bool TaskSlowdown() = 0;
+  virtual bool TaskDone() = 0;
+};
+
 // A task which can be run by a TaskGraphRunner. To run a Task, it should be
 // inserted into a TaskGraph, which can then be scheduled on the
 // TaskGraphRunner.
 class CC_EXPORT Task : public base::RefCountedThreadSafe<Task> {
  public:
   typedef std::vector<scoped_refptr<Task>> Vector;
 
   // 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;
 
+  TaskWorker* GetTaskWorker() { return worker_; }
+  void AttachTaskWorker(TaskWorker* worker);
+  void DetachTaskWorker();
+
   void WillRun();
   void DidRun();
   bool HasFinishedRunning() const;
 
  protected:
   friend class base::RefCountedThreadSafe<Task>;
 
   Task();
   virtual ~Task();
 
+  TaskWorker* worker_;
   bool will_run_;
   bool did_run_;
 };
 
+class CC_EXPORT AutoDetachTaskWorker {
+ public:
+  explicit AutoDetachTaskWorker(Task& task, TaskWorker* worker) : task_(task) {
+    DCHECK(worker);
+    task_.AttachTaskWorker(worker);
+  }
+
+  ~AutoDetachTaskWorker() { task_.DetachTaskWorker(); }
+
+ private:
+  Task& task_;
+  DISALLOW_COPY_AND_ASSIGN(AutoDetachTaskWorker);
+};
+
 // A task dependency graph describes the order in which to execute a set
 // of tasks. Dependencies are represented as edges. Each node is assigned
 // a category, a priority and a run count that matches the number of
 // dependencies. Priority range from 0 (most favorable scheduling) to UINT16_MAX
 // (least favorable). Categories range from 0 to UINT16_MAX. It is up to the
 // implementation and its consumer to determine the meaning (if any) of a
 // category. A TaskGraphRunner implementation may chose to prioritize certain
 // categories over others, regardless of the individual priorities of tasks.
 struct CC_EXPORT TaskGraph {
   struct Node {
@@ skipping 157 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_