Add base::test::ScopedTaskEnvironment::RunUntilIdle().

base/test/scoped_task_environment.h

 // Copyright 2017 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 BASE_TEST_SCOPED_TASK_ENVIRONMENT_H_
 #define BASE_TEST_SCOPED_TASK_ENVIRONMENT_H_
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 
 namespace base {
 
 class TaskScheduler;
 
 namespace test {
 
 // ScopedTaskEnvironment allows usage of these APIs within its scope:
 // - (Thread|Sequenced)TaskRunnerHandle, on the thread where it lives
 // - base/task_scheduler/post_task.h, on any thread
 //
 // Tests that need either of these APIs should instantiate a
 // ScopedTaskEnvironment.
 //
 // Tasks posted to the (Thread|Sequenced)TaskRunnerHandle run synchronously when
-// RunLoop::Run(UntilIdle) is called on the thread where the
-// ScopedTaskEnvironment lives.
+// RunLoop::Run(UntilIdle) or ScopedTaskEnvironment::RunUntilIdle is called on

[robliao, 2017/05/09 21:52:52]

Nit: RunUntilIdle()

+// the thread where the ScopedTaskEnvironment lives.
 //
 // Tasks posted through base/task_scheduler/post_task.h run on dedicated threads
 // as they are posted.
 //
+// All methods of ScopedTaskEnvironment must be called from the same thread.
+//
 // Usage:
 //
 //   class MyTestFixture : public testing::Test {
 //    public:
 //     (...)
 //
 //    protected:
 //     // Must be the first member (or at least before any member that cares
 //     // about tasks) to be initialized first and destroyed last. protected
 //     // instead of private visibility will allow controlling the task
@@ skipping 18 matching lines @@
   };
 
   ScopedTaskEnvironment(
       MainThreadType main_thread_type = MainThreadType::DEFAULT);
 
   // Runs pending (Thread|Sequenced)TaskRunnerHandle tasks and pending
   // BLOCK_SHUTDOWN TaskScheduler tasks. Then, unregisters the TaskScheduler and
   // the (Thread|Sequenced)TaskRunnerHandle.
   ~ScopedTaskEnvironment();
 
+  // Synchronously runs (Thread|Sequenced)TaskRunnerHandle tasks until no
+  // undelayed (Thread|Sequenced)TaskRunnerHandle or TaskScheduler tasks remain.
+  void RunUntilIdle();
+
  private:
   // Note: |message_loop_| is an implementation detail and will be replaced in
   // the future, do NOT rely on the presence of a MessageLoop beyond
   // (Thread|Sequenced)TaskRunnerHandle and RunLoop.
   MessageLoop message_loop_;
 
   const TaskScheduler* task_scheduler_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedTaskEnvironment);
 };
 
 }  // namespace test
 }  // namespace base
 
 #endif  // BASE_TEST_SCOPED_ASYNC_TASK_SCHEDULER_H_