Upstream RunBlockingPoolTask().

content/public/test/test_utils.cc

Index: content/public/test/test_utils.cc
diff --git a/content/public/test/test_utils.cc b/content/public/test/test_utils.cc
index ae45762dab52550be6d1c7008b24dc8b224f5bf0..890e97a83728106b73510573b95d8c7521fd2da1 100644
--- a/content/public/test/test_utils.cc
+++ b/content/public/test/test_utils.cc
@@ -49,7 +49,7 @@ void RunAllPendingMessageAndSendQuit(BrowserThread::ID thread_id,
   BrowserThread::PostTask(thread_id, FROM_HERE, quit_task);
 }
 
-// Class used handle result callbacks for ExecuteScriptAndGetValue.
+// Class used to handle result callbacks for ExecuteScriptAndGetValue.
 class ScriptCallback {
  public:
   ScriptCallback() { }
@@ -70,6 +70,27 @@ void ScriptCallback::ResultCallback(const base::Value* result) {
   base::MessageLoop::current()->Quit();
 }
 
+// Monitors if any task is posted to a message loop.
+class TaskObserver : public base::MessageLoop::TaskObserver {
+ public:
+  TaskObserver() : posted_(false) {}
+  virtual ~TaskObserver() {}
+
+  // MessageLoop::TaskObserver overrides.
+  virtual void WillProcessTask(const base::PendingTask& pending_task) OVERRIDE {
+  }
+  virtual void DidProcessTask(const base::PendingTask& pending_task) OVERRIDE {
+    posted_ = true;
+  }
+
+  // Returns true if any task was posted.
+  bool posted() const { return posted_; }
+
+ private:
+  bool posted_;
+  DISALLOW_COPY_AND_ASSIGN(TaskObserver);
+};
+
 // Adapter that makes a WindowedNotificationObserver::ConditionTestCallback from
 // a WindowedNotificationObserver::ConditionTestCallbackWithoutSourceAndDetails
 // by ignoring the notification source and details.
@@ -129,6 +150,20 @@ void RunAllPendingInMessageLoop(BrowserThread::ID thread_id) {
   RunThisRunLoop(&run_loop);
 }
 
+void RunAllBlockingPoolTasksUntilIdle() {
+  while (true) {
+    content::BrowserThread::GetBlockingPool()->FlushForTesting();
+
+    TaskObserver task_observer;

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

It seems like you want to know if any tasks are added while flushing the
blocking pool. I would have expected the TaskObserver to be added before the
flush.

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

Done.

[hashimoto, 2014/07/15 05:17:41]

No need to start observing the message loop while flushing the blocking pool.
The observer is not to know if any tasks are added while flushing.
task_observer.posted() returns true if the message loop processes any tasks
during RunUntilIdle().

Perhaps, we should rename posted() to something like "processed_any_task" to
make it clear.

[mtomasz, 2014/07/15 05:45:29]

Done.

+    base::MessageLoop::current()->AddTaskObserver(&task_observer);
+    base::RunLoop().RunUntilIdle();
+    base::MessageLoop::current()->RemoveTaskObserver(&task_observer);
+
+    if (!task_observer.posted())
+      break;
+  }
+}
+
 base::Closure GetQuitTaskForRunLoop(base::RunLoop* run_loop) {
   return base::Bind(&DeferredQuitRunLoop, run_loop->QuitClosure(),
                     kNumQuitDeferrals);