Upstream RunBlockingPoolTask().

content/public/test/test_utils.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_TEST_TEST_UTILS_H_
 #define CONTENT_PUBLIC_TEST_TEST_UTILS_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/run_loop.h"
 #include "content/public/browser/browser_child_process_observer.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 
 namespace base {
 class Value;
-}
+}  // namespace base
 
 // A collection of functions designed for use with unit and browser tests.
 
 namespace content {
 
 class RenderFrameHost;
 
 // Turns on nestable tasks, runs the message loop, then resets nestable tasks
 // to what they were originally. Prefer this over MessageLoop::Run for in
 // process browser tests that need to block until a condition is met.
 void RunMessageLoop();
 
 // Variant of RunMessageLoop that takes RunLoop.
 void RunThisRunLoop(base::RunLoop* run_loop);
 
 // Turns on nestable tasks, runs all pending tasks in the message loop,
 // then resets nestable tasks to what they were originally. Prefer this
 // over MessageLoop::RunAllPending for in process browser tests to run
 // all pending tasks.
 void RunAllPendingInMessageLoop();
 
 // Blocks the current thread until all the pending messages in the loop of the
 // thread |thread_id| have been processed.
 void RunAllPendingInMessageLoop(BrowserThread::ID thread_id);
 
+// Runs all tasks posted to the blocking pool, including subsequent tasks posted

[sky, 2014/07/11 16:37:54]

You're description seems overly complicated, maybe:
Runs until both the blocking pool and the current message loop are empty (have
no more scheduled tasks).

[mtomasz, 2014/07/14 07:33:57]

Done.

+// to the UI message loop and the blocking pool.
+//
+// A task is often posted to the blocking pool with PostTaskAndReply(). In
+// that case, a task is posted back to the UI message loop, which can again
+// post a task to the blocking pool. This function processes these tasks
+// repeatedly.
+void RunAllBlockingPoolTasksUntilIdle();
+
 // Get task to quit the given RunLoop. It allows a few generations of pending
 // tasks to run as opposed to run_loop->QuitClosure().
 base::Closure GetQuitTaskForRunLoop(base::RunLoop* run_loop);
 
 // Executes the specified JavaScript in the specified frame, and runs a nested
 // MessageLoop. When the result is available, it is returned.
 // This should not be used; the use of the ExecuteScript functions in
 // browser_test_utils is preferable.
 scoped_ptr<base::Value> ExecuteScriptAndGetValue(
     RenderFrameHost* render_frame_host, const std::string& script);
@@ skipping 151 matching lines @@
 
   int child_thread_count_;
   scoped_refptr<MessageLoopRunner> runner_;
 
   DISALLOW_COPY_AND_ASSIGN(InProcessUtilityThreadHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_TEST_UTILS_H_