TaskScheduler: Add TaskRunnerHandle support to TaskScheduler tasks

base/threading/sequenced_task_runner_handle.h

Index: base/threading/sequenced_task_runner_handle.h
diff --git a/base/threading/sequenced_task_runner_handle.h b/base/threading/sequenced_task_runner_handle.h
index 7084ec4bb9bf879caad480e9393bb70d05756b43..7dd6974fed18a35fecea772aeb67e944524384fa 100644
--- a/base/threading/sequenced_task_runner_handle.h
+++ b/base/threading/sequenced_task_runner_handle.h
@@ -22,13 +22,22 @@ class BASE_EXPORT SequencedTaskRunnerHandle {
   static scoped_refptr<SequencedTaskRunner> Get();
 
   // Returns true if one of the following conditions is fulfilled:
-  // a) The current thread has a ThreadTaskRunnerHandle (which includes any
+  // a) A SequencedTaskRunner has been assigned to the current thread by
+  //    instantiating a SequencedTaskRunnerHandle.
+  // b) The current thread has a ThreadTaskRunnerHandle (which includes any
   //    thread that has a MessageLoop associated with it), or
-  // b) The current thread is a worker thread belonging to a
+  // c) The current thread is a worker thread belonging to a
   //    SequencedWorkerPool.
   static bool IsSet();
 
+  // Binds |task_runner| to the current thread.
+  explicit SequencedTaskRunnerHandle(
+      scoped_refptr<SequencedTaskRunner> task_runner);
+  ~SequencedTaskRunnerHandle();
+
  private:
+  scoped_refptr<SequencedTaskRunner> task_runner_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(SequencedTaskRunnerHandle);

[fdoray, 2016/04/22 14:43:12]

DISALLOW_IMPLICIT_CONSTRUCTORS should be used "for a class that wants to prevent
anyone from instantiating it". I think you should use DISALLOW_COPY_AND_ASSIGN
even though it doesn't change anything in practice.
 
https://code.google.com/p/chromium/codesearch#chromium/src/base/macros.h&l=34

[gab, 2016/04/25 18:31:52]

Good point, DISALLOW_IMPLICIT_CONSTRUCTORS made sense before this CL, but now
that it can be instantiated DISALLOW_COPY_AND_ASSIGN is the right thing. Also
added it to ThreadTaskRunnerHandle.

 };