Add FlushForTesting to base::Thread.

base/threading/thread.cc

 // 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.
 
 #include "base/threading/thread.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
@@ skipping 126 matching lines @@
 
 bool Thread::WaitUntilThreadStarted() const {
   DCHECK(owning_sequence_checker_.CalledOnValidSequence());
   if (!message_loop_)
     return false;
   base::ThreadRestrictions::ScopedAllowWait allow_wait;
   start_event_.Wait();
   return true;
 }
 
+void Thread::FlushForTesting() {

[danakj, 2016/09/15 18:09:33]

I'd prefer a free function in base/test/ actually. There's no reason this has to
be on Thread right?

[gab, 2016/09/15 20:18:33]

Maybe discoverability is a reason? i.e. I just realized that such a thing
already more or less exists
(https://cs.chromium.org/chromium/src/base/test/thread_test_helper.h) ...
whereas I've always seen "FlushForTesting" methods on APIs themselves and never
thought of looking in base/test for this.

WDYT?

+  DCHECK(owning_sequence_checker_.CalledOnValidSequence());
+  if (!message_loop_)
+    return;
+
+  WaitableEvent done(WaitableEvent::ResetPolicy::AUTOMATIC,
+                     WaitableEvent::InitialState::NOT_SIGNALED);
+  task_runner()->PostTask(FROM_HERE,
+                          Bind(&WaitableEvent::Signal, Unretained(&done)));
+  done.Wait();
+}
+
 void Thread::Stop() {
   DCHECK(joinable_);
 
   // TODO(gab): Fix improper usage of this API (http://crbug.com/629139) and
   // enable this check, until then synchronization with Start() via
   // |thread_lock_| is required...
   // DCHECK(owning_sequence_checker_.CalledOnValidSequence());
   AutoLock lock(thread_lock_);
 
   StopSoon();
@@ skipping 174 matching lines @@
   run_loop_ = nullptr;
 }
 
 void Thread::ThreadQuitHelper() {
   DCHECK(run_loop_);
   run_loop_->QuitWhenIdle();
   SetThreadWasQuitProperly(true);
 }
 
 }  // namespace base