cc: Rasterize cheap tiles immediately

cc/worker_pool.h

Index: cc/worker_pool.h
diff --git a/cc/worker_pool.h b/cc/worker_pool.h
index f47dd70b9981b23af18184c6c3f0ea911b051c12..599ea590aa59a1917908e297f75a5dad8e7272e8 100644
--- a/cc/worker_pool.h
+++ b/cc/worker_pool.h
@@ -24,6 +24,8 @@ class WorkerPoolTask {
 
   virtual void Run(RenderingStats* rendering_stats) = 0;
 
+  virtual void DeferToThread(base::Thread* thread) = 0;
+
   void Completed();
 
  protected:
@@ -64,6 +66,15 @@ class WorkerPool {
   // Collect rendering stats all completed tasks.
   void GetRenderingStats(RenderingStats* stats);
 
+  // Run cheap, low latency tasks on the main thread. If the pending cheap tasks
+  // take too long to run, the remaining ones are deferred to the worker
+  // threads. Returns true if any cheap tasks were run.
+  bool RunCheapTasks();
+
+  // Control whether cheap (main thread) tasks are allowed to be queued for
+  // execution.
+  void SetCheapTasksAllowed(bool allowed);

[reveman, 2013/02/13 22:17:36]

would it be possible to leave this in the tile manager and just not post tasks
with is_cheap=true if they are not allowed?

+
  protected:
   class Worker : public base::Thread {
    public:
@@ -103,6 +114,8 @@ class WorkerPool {
   explicit WorkerPool(size_t num_threads);
 
   WorkerPool::Worker* GetWorkerForNextTask();
+  bool CanPostCheapTask() const;
+  void PostCheapTask(scoped_ptr<internal::WorkerPoolTask> task);
 
  private:
   class NumPendingTasksComparator {
@@ -120,6 +133,11 @@ class WorkerPool {
   bool workers_need_sorting_;
   bool shutdown_;
 
+  bool cheap_tasks_allowed_;
+  bool running_cheap_tasks_;
+  ScopedPtrDeque<internal::WorkerPoolTask> pending_cheap_tasks_;
+  scoped_ptr<RenderingStats> cheap_rendering_stats_;
+
   DISALLOW_COPY_AND_ASSIGN(WorkerPool);
 };