Experiment with redirecting all BrowserThreads (but UI/IO) to TaskScheduler

content/public/test/test_browser_thread.cc

 // Copyright (c) 2011 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 "content/public/test/test_browser_thread.h"
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/threading/thread.h"
 #include "content/browser/browser_thread_impl.h"
@@ skipping 22 matching lines @@
     BrowserThreadImpl::CleanUp();
   }
 
  private:
   std::unique_ptr<NotificationService> notification_service_;
 
   DISALLOW_COPY_AND_ASSIGN(TestBrowserThreadImpl);
 };
 
 TestBrowserThread::TestBrowserThread(BrowserThread::ID identifier)
-    : impl_(new TestBrowserThreadImpl(identifier)) {
-}
+    : impl_(new TestBrowserThreadImpl(identifier)), identifier_(identifier) {}
 
 TestBrowserThread::TestBrowserThread(BrowserThread::ID identifier,
                                      base::MessageLoop* message_loop)
-    : impl_(new TestBrowserThreadImpl(identifier, message_loop)) {}
+    : impl_(new TestBrowserThreadImpl(identifier, message_loop)),
+      identifier_(identifier) {}
 
 TestBrowserThread::~TestBrowserThread() {
-  Stop();
+  // The upcoming BrowserThreadImpl::ResetGlobalsForTesting() call requires that
+  // |impl_| have triggered the shutdown phase for its BrowserThread::ID. This
+  // either happens when the thread is stopped (if real) or destroyed (when fake
+  // -- i.e. using an externally provided MessageLoop).
+  impl_.reset();
+
+  // Resets BrowserThreadImpl globals binding |identifier_| to |impl_|. This is

[robliao, 2016/12/08 01:57:17]

How does the below set the binding from |identifier_| to |impl_|?

ResetGlobalForTesting looks like it just clears everything.

[gab, 2016/12/08 18:49:41]

I meant to say that it clears that very binding, reworded.

+  // fine since the underlying MessageLoop has already been flushed and deleted
+  // in Stop(). In the case of an externally provided MessageLoop however, this
+  // means that TaskRunners obtained through
+  // |BrowserThreadImpl::GetTaskRunnerForThread(identifier_)| will no longer
+  // recognize their BrowserThreadImpl for RunsTasksOnCurrentThread(). This
+  // happens most often when such verifications are made from
+  // MessageLoop::DestructionObservers. Callers that care to work around that
+  // should instead use this shutdown sequence: TestBrowserThread::Stop() ->

[robliao, 2016/12/08 01:57:17]

Nit: Might be easier to read this as a sequenced list.

[gab, 2016/12/08 18:49:41]

Done.

+  // ~MessageLoop() -> ~TestBrowserThread() (~TestBrowserThreadBundle() does
+  // this).
+  BrowserThreadImpl::ResetGlobalsForTesting(identifier_);
 }
 
 bool TestBrowserThread::Start() {
   return impl_->Start();
 }
 
 bool TestBrowserThread::StartAndWaitForTesting() {
   return impl_->StartAndWaitForTesting();
 }
 
 bool TestBrowserThread::StartIOThread() {
   base::Thread::Options options;
   options.message_loop_type = base::MessageLoop::TYPE_IO;
   return impl_->StartWithOptions(options);
 }
 
 void TestBrowserThread::Stop() {
   impl_->Stop();
 }
 
 bool TestBrowserThread::IsRunning() {
   return impl_->IsRunning();
 }
 
 }  // namespace content