Added stub MediaSourcePlayer for developing behind the flag

base/threading/non_thread_safe.h

 // 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.
 
 #ifndef BASE_THREADING_NON_THREAD_SAFE_H_
 #define BASE_THREADING_NON_THREAD_SAFE_H_
 
 // Classes deriving from NonThreadSafe may need to suppress MSVC warning 4275:
 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
 // There is a specific macro to do it: NON_EXPORTED_BASE(), defined in
@@ skipping 40 matching lines @@
 //     DCHECK(CalledOnValidThread());
 //     ... (do stuff) ...
 //   }
 // }
 //
 // Note that base::ThreadChecker offers identical functionality to
 // NonThreadSafe, but does not require inheritance. In general, it is preferable
 // to have a base::ThreadChecker as a member, rather than inherit from
 // NonThreadSafe. For more details about when to choose one over the other, see
 // the documentation for base::ThreadChecker.
-#if ENABLE_NON_THREAD_SAFE
+#if defined(DISABLE_NON_THREAD_SAFE)

[qinmin, 2015/04/27 22:16:20]

why we need this here? 

+typedef NonThreadSafeDoNothing NonThreadSafe;
+#elif defined(ENABLE_NON_THREAD_SAFE)
 typedef NonThreadSafeImpl NonThreadSafe;
 #else
 typedef NonThreadSafeDoNothing NonThreadSafe;
 #endif  // ENABLE_NON_THREAD_SAFE
 
 #undef ENABLE_NON_THREAD_SAFE
 
 }  // namespace base
 
 #endif  // BASE_THREADING_NON_THREAD_SAFE_H_