Add REAL_TASK_SCHEDULER option in TestBrowserThreadBundle.

content/public/test/test_browser_thread_bundle.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.
 
 // TestBrowserThreadBundle is a convenience class for creating a set of
 // TestBrowserThreads, a blocking pool, and a task scheduler in unit tests. For
 // most tests, it is sufficient to just instantiate the TestBrowserThreadBundle
 // as a member variable. It is a good idea to put the TestBrowserThreadBundle as
 // the first member variable in test classes, so it is destroyed last, and the
 // test threads always exist from the perspective of other classes.
 //
 // By default, all of the created TestBrowserThreads and the task scheduler will
 // be backed by a single shared MessageLoop. If a test truly needs separate
 // threads, it can do so by passing the appropriate combination of option values
 // during the TestBrowserThreadBundle construction.
 //
 // To synchronously run tasks posted to task scheduler or to TestBrowserThreads
 // that use the shared MessageLoop, call RunLoop::Run/RunUntilIdle() on the
 // thread where the TestBrowserThreadBundle lives. The destructor of
 // TestBrowserThreadBundle runs remaining TestBrowserThreads tasks, remaining
 // blocking pool tasks, and remaining BLOCK_SHUTDOWN task scheduler tasks.
 //
 // If a test needs a MessageLoopForIO on the main thread, it should use the
 // IO_MAINLOOP option. This also allows task scheduler tasks to use
 // FileDescriptorWatcher. Most of the time, IO_MAINLOOP avoids needing to use a
 // REAL_IO_THREAD.
 //
+// If a test needs a TaskScheduler that runs tasks on a dedicated thread, it
+// should use REAL_TASK_SCHEDULER. Usage of this option should be justified as
+// it is easier to understand and debug a single-threaded unit test.
+//
 // For some tests it is important to emulate real browser startup. During real
 // browser startup, the main MessageLoop is created before other threads.
 // Passing DONT_CREATE_THREADS to constructor will delay creating other threads
 // until the test explicitly calls CreateThreads().
 //
 // DONT_CREATE_THREADS should only be used when the options specify at least
 // one real thread other than the main thread.
 
 #ifndef CONTENT_PUBLIC_TEST_TEST_BROWSER_THREAD_BUNDLE_H_
 #define CONTENT_PUBLIC_TEST_TEST_BROWSER_THREAD_BUNDLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 
 namespace base {
 class MessageLoop;
 namespace test {
+class ScopedAsyncTaskScheduler;
 class ScopedTaskScheduler;
 }  // namespace test
 }  // namespace base
 
 namespace content {
 
 class TestBrowserThread;
 
 class TestBrowserThreadBundle {
  public:
   // Used to specify the type of MessageLoop that backs the UI thread, and
   // which of the named BrowserThreads should be backed by a real
   // threads. The UI thread is always the main thread in a unit test.
   enum Options {
-    DEFAULT = 0x00,
-    IO_MAINLOOP = 0x01,
-    REAL_DB_THREAD = 0x02,
-    REAL_FILE_THREAD = 0x08,
-    REAL_IO_THREAD = 0x10,
-    DONT_CREATE_THREADS = 0x20,
+    DEFAULT = 0,
+    IO_MAINLOOP = 1 << 0,

[robliao, 2017/01/12 21:36:01]

While we're here, might be worthwhile to comment that 1 << 1 is unused.
Otherwise, it looks like a bug.

Reference: 1 << 1 used to be REAL_WEBKIT_DEPRECATED_THREAD.
https://codereview.chromium.org/18414007/diff/15001/content/public/test/test_...

Given this is just test code, it might be okay to just reenumerate this, but
that would be beyond the scope of this CL. I'll leave it up to you.

[fdoray, 2017/01/13 13:11:45]

Done. Reenumerated. There is no good reason not to reuse the bit previously used
by REAL_WEBKIT_DEPRECATED_THREAD.

+    REAL_DB_THREAD = 1 << 2,
+    REAL_FILE_THREAD = 1 << 3,
+    REAL_IO_THREAD = 1 << 4,
+    REAL_TASK_SCHEDULER = 1 << 5,
+    DONT_CREATE_THREADS = 1 << 6,
   };
 
   TestBrowserThreadBundle();
   explicit TestBrowserThreadBundle(int options);
 
   // Creates threads; should only be called from other classes if the
   // DONT_CREATE_THREADS option was used when the bundle was created.
   void CreateThreads();
 
   ~TestBrowserThreadBundle();
 
  private:
   void Init();
 
   std::unique_ptr<base::MessageLoop> message_loop_;
-  std::unique_ptr<base::test::ScopedTaskScheduler> task_scheduler_;
+  std::unique_ptr<base::test::ScopedAsyncTaskScheduler>
+      scoped_async_task_scheduler_;
+  std::unique_ptr<base::test::ScopedTaskScheduler> scoped_task_scheduler_;
   std::unique_ptr<TestBrowserThread> ui_thread_;
   std::unique_ptr<TestBrowserThread> db_thread_;
   std::unique_ptr<TestBrowserThread> file_thread_;
   std::unique_ptr<TestBrowserThread> file_user_blocking_thread_;
   std::unique_ptr<TestBrowserThread> process_launcher_thread_;
   std::unique_ptr<TestBrowserThread> cache_thread_;
   std::unique_ptr<TestBrowserThread> io_thread_;
 
   int options_;
   bool threads_created_;
 
   DISALLOW_COPY_AND_ASSIGN(TestBrowserThreadBundle);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_TEST_BROWSER_THREAD_BUNDLE_H_