Use base::Thread instead of single-threaded SequencedWorkerPool in TestLauncher.

base/test/launcher/test_launcher.h

 // 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.
 
 #ifndef BASE_TEST_LAUNCHER_TEST_LAUNCHER_H_
 #define BASE_TEST_LAUNCHER_TEST_LAUNCHER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 14 matching lines @@
 class TestCase;
 class TestInfo;
 }
 
 namespace base {
 
 class CommandLine;
 struct LaunchOptions;
 class SequencedWorkerPoolOwner;
 class TestLauncher;
+class Thread;
 
 // Constants for GTest command-line flags.
 extern const char kGTestFilterFlag[];
 extern const char kGTestFlagfileFlag[];
 extern const char kGTestHelpFlag[];
 extern const char kGTestListTestsFlag[];
 extern const char kGTestRepeatFlag[];
 extern const char kGTestRunDisabledTestsFlag[];
 extern const char kGTestOutputFlag[];
 
@@ skipping 113 matching lines @@
       const TimeDelta& elapsed_time,
       bool was_timeout,
       const std::string& output);
 
   // Called when a test iteration is finished.
   void OnTestIterationFinished();
 
   // Called by the delay timer when no output was made for a while.
   void OnOutputTimeout();
 
+  // Returns the TaskRunner to be used to launch child test processes. This
+  // TaskRunner will have TaskShutdownBehavior::BLOCK_SHUTDOWN semantics.
+  scoped_refptr<TaskRunner> GetTaskRunner();
+
   // Make sure we don't accidentally call the wrong methods e.g. on the worker
   // pool thread. With lots of callbacks used this is non-trivial.
   // Should be the first member so that it's destroyed last: when destroying
   // other members, especially the worker pool, we may check the code is running
   // on the correct thread.
   ThreadChecker thread_checker_;
 
   TestLauncherDelegate* launcher_delegate_;
 
   // Support for outer sharding, just like gtest does.
@@ skipping 42 matching lines @@
   bool run_result_;
 
   TestResultsTracker results_tracker_;
 
   // Watchdog timer to make sure we do not go without output for too long.
   DelayTimer watchdog_timer_;
 
   // Number of jobs to run in parallel.
   size_t parallel_jobs_;
 
-  // Worker pool used to launch processes in parallel.
+  // Worker pool used to launch processes in parallel (|worker_thread_| is used
+  // instead if |parallel_jobs == 1|).
   std::unique_ptr<SequencedWorkerPoolOwner> worker_pool_owner_;
+  std::unique_ptr<Thread> worker_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(TestLauncher);
 };
 
 // Extract part from |full_output| that applies to |result|.
 std::string GetTestOutputSnippet(const TestResult& result,
                                  const std::string& full_output);
 
 }  // namespace base
 
 #endif  // BASE_TEST_LAUNCHER_TEST_LAUNCHER_H_