Make MessageLoopProxy::current() usable on threads that don't have MessageLoop.

base/message_loop_unittest.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 <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/compiler_specific.h"
 #include "base/eintr_wrapper.h"
@@ skipping 1671 matching lines @@
       base::Bind(&DestructionObserverProbe::Run,
                  new DestructionObserverProbe(&task_destroyed,
                                               &destruction_observer_called)),
       kDelay);
   delete loop;
   EXPECT_TRUE(observer.task_destroyed_before_message_loop());
   // The task should have been destroyed when we deleted the loop.
   EXPECT_TRUE(task_destroyed);
   EXPECT_TRUE(destruction_observer_called);
 }
+
+// Verify that MessageLoop sets ThreadMainTaskRunner::current() and it
+// posts tasks on that message loop.
+TEST(MessageLoopTest, ThreadMainTaskRunner) {
+  MessageLoop loop;
+
+  scoped_refptr<Foo> foo(new Foo());
+  std::string a("a");
+  base::ThreadMainTaskRunner::current()->PostTask(FROM_HERE, base::Bind(
+      &Foo::Test1ConstRef, foo.get(), a));
+
+  // Post quit task;
+  MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
+      &MessageLoop::Quit, base::Unretained(MessageLoop::current())));
+
+  // Now kick things off
+  MessageLoop::current()->Run();
+
+  EXPECT_EQ(foo->test_count(), 1);
+  EXPECT_EQ(foo->result(), "a");
+}