Fix a race in HandleWatcherTest and remove suppression.

mojo/message_pump/handle_watcher_unittest.cc

 // Copyright 2013 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 "mojo/message_pump/handle_watcher.h"
 
 #include <string>
 
 #include "base/at_exit.h"
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/run_loop.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "base/threading/thread.h"
 #include "mojo/message_pump/message_pump_mojo.h"
 #include "mojo/message_pump/time_helper.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/public/cpp/test_support/test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 91 matching lines @@
   base::RunLoop* run_loop_;
 
   base::WeakPtrFactory<CallbackHelper> weak_factory_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CallbackHelper);
 };
 
 class HandleWatcherTest : public testing::TestWithParam<MessageLoopConfig> {
  public:
-  HandleWatcherTest() : message_loop_(CreateMessageLoop(GetParam())) {}
+  HandleWatcherTest()
+      : at_exit_(new base::ShadowingAtExitManager),
+        message_loop_(CreateMessageLoop(GetParam())) {}
   virtual ~HandleWatcherTest() {
+    // By explicitly destroying |at_exit_| before resetting the tick clock, it
+    // ensures that the handle watcher thread (if there is one) is shut down,
+    // preventing a race with users of the tick clock in MessagePumpMojo.
+    at_exit_.reset();
     test::SetTickClockForTest(NULL);
   }
 
  protected:
   void TearDownMessageLoop() {
     message_loop_.reset();
   }
 
+  // This should be called at the beginning of any test that needs it, so that
+  // it is installed before the handle watcher thread starts.
   void InstallTickClock() {
     test::SetTickClockForTest(&tick_clock_);
   }
 
   base::SimpleTestTickClock tick_clock_;
 
  private:
-  base::ShadowingAtExitManager at_exit_;
+  scoped_ptr<base::ShadowingAtExitManager> at_exit_;
   scoped_ptr<base::MessageLoop> message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(HandleWatcherTest);
 };
 
 INSTANTIATE_TEST_CASE_P(
     MultipleMessageLoopConfigs, HandleWatcherTest,
     testing::Values(MESSAGE_LOOP_CONFIG_DEFAULT, MESSAGE_LOOP_CONFIG_MOJO));
 
 // Trivial test case with a single handle to watch.
@@ skipping 323 matching lines @@
                               message_loop.task_runner(),
                               &run_loop, &threads_active_counter));
   }
   run_loop.Run();
   ASSERT_EQ(0, threads_active_counter);
 }
 
 }  // namespace test
 }  // namespace common
 }  // namespace mojo