scheduler: Implement task observers

content/child/webthread_impl.h

Index: content/child/webthread_impl.h
diff --git a/content/child/webthread_impl.h b/content/child/webthread_impl.h
index ba2888f9bc70b007789d3f8ce022234ec45c3f33..edd39566e81dc79fc13373c1e1bf2db87d521049 100644
--- a/content/child/webthread_impl.h
+++ b/content/child/webthread_impl.h
@@ -22,18 +22,43 @@ class CONTENT_EXPORT WebThreadBase : public blink::WebThread {
  public:
   virtual ~WebThreadBase();
 
+  // blink::WebThread implementation.
+  virtual bool isCurrentThread() const;
+  virtual blink::PlatformThreadId threadId() const = 0;
+
+  virtual void postTask(const blink::WebTraceLocation& location, Task* task);
+  virtual void postDelayedTask(const blink::WebTraceLocation& location,
+                               Task* task,
+                               long long delay_ms);
+
+  virtual void enterRunLoop();
+  virtual void exitRunLoop();
+
   virtual void addTaskObserver(TaskObserver* observer);
   virtual void removeTaskObserver(TaskObserver* observer);
 
-  virtual bool isCurrentThread() const = 0;
-  virtual blink::PlatformThreadId threadId() const = 0;
+  // Returns the base::Bind-compatible task runner for posting tasks to this
+  // thread. Can be called from any thread.
+  virtual base::SingleThreadTaskRunner* TaskRunner() const = 0;
 
  protected:
+  class TaskObserverAdapter;
+
   WebThreadBase();
 
- private:
-  class TaskObserverAdapter;
+  // Returns the underlying MessageLoop for this thread. Only used for entering
+  // and exiting a nested run loop. Only called on the thread that the
+  // WebThread belongs to.
+  virtual base::MessageLoop* MessageLoop() const = 0;
+
+  virtual void AddTaskObserverInternal(
+      base::MessageLoop::TaskObserver* observer);
+  virtual void RemoveTaskObserverInternal(
+      base::MessageLoop::TaskObserver* observer);
+
+  static void RunWebThreadTask(scoped_ptr<blink::WebThread::Task> task);
 
+ private:
   typedef std::map<TaskObserver*, TaskObserverAdapter*> TaskObserverMap;
   TaskObserverMap task_observer_map_;
 };
@@ -43,24 +68,15 @@ class CONTENT_EXPORT WebThreadImpl : public WebThreadBase {
   explicit WebThreadImpl(const char* name);
   virtual ~WebThreadImpl();
 
-  virtual void postTask(const blink::WebTraceLocation& location, Task* task);
-  virtual void postDelayedTask(const blink::WebTraceLocation& location,
-                               Task* task,
-                               long long delay_ms);
-
-  // TODO(skyostil): Remove once blink has migrated.
-  virtual void postTask(Task* task);
-  virtual void postDelayedTask(Task* task, long long delay_ms);
-
-  virtual void enterRunLoop();
-  virtual void exitRunLoop();
-
-  base::MessageLoop* message_loop() const { return thread_->message_loop(); }
+  // blink::WebThread implementation.
+  blink::PlatformThreadId threadId() const override;
 
-  virtual bool isCurrentThread() const override;
-  virtual blink::PlatformThreadId threadId() const override;
+  // WebThreadBase implementation.
+  base::SingleThreadTaskRunner* TaskRunner() const override;
 
  private:
+  base::MessageLoop* MessageLoop() const override;
+
   scoped_ptr<base::Thread> thread_;
 };
 
@@ -70,21 +86,14 @@ class WebThreadImplForMessageLoop : public WebThreadBase {
       scoped_refptr<base::SingleThreadTaskRunner> owning_thread_task_runner);
   CONTENT_EXPORT virtual ~WebThreadImplForMessageLoop();
 
-  virtual void postTask(const blink::WebTraceLocation& location, Task* task);
-  virtual void postDelayedTask(const blink::WebTraceLocation& location,
-                               Task* task,
-                               long long delay_ms);
-
-  // TODO(skyostil): Remove once blink has migrated.
-  virtual void postTask(Task* task);
-  virtual void postDelayedTask(Task* task, long long delay_ms);
+  // blink::WebThread implementation.
+  blink::PlatformThreadId threadId() const override;
 
-  virtual void enterRunLoop() override;
-  virtual void exitRunLoop() override;
+  // WebThreadBase implementation.
+  base::MessageLoop* MessageLoop() const override;
 
  private:
-  virtual bool isCurrentThread() const override;
-  virtual blink::PlatformThreadId threadId() const override;
+  base::SingleThreadTaskRunner* TaskRunner() const override;
 
   scoped_refptr<base::SingleThreadTaskRunner> owning_thread_task_runner_;
   blink::PlatformThreadId thread_id_;