Make base::Timer sequence-friendly.

media/base/android/media_codec_loop.h

Index: media/base/android/media_codec_loop.h
diff --git a/media/base/android/media_codec_loop.h b/media/base/android/media_codec_loop.h
index 2ee738cf1c5ab03062b947121ada0f82461e8c46..02dbb669b78c9366b0c294de062813ec070744f9 100644
--- a/media/base/android/media_codec_loop.h
+++ b/media/base/android/media_codec_loop.h
@@ -11,7 +11,9 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ -101,10 +103,6 @@
 //    |             |
 // [Ready]       [Error]
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace media {
 
 class MEDIA_EXPORT MediaCodecLoop {
@@ -204,8 +202,7 @@ class MEDIA_EXPORT MediaCodecLoop {
   MediaCodecLoop(int sdk_level,
                  Client* client,
                  std::unique_ptr<MediaCodecBridge> media_codec,
-                 scoped_refptr<base::SingleThreadTaskRunner> =
-                     scoped_refptr<base::SingleThreadTaskRunner>());
+                 scoped_refptr<base::SingleThreadTaskRunner> = nullptr);

[DaleCurtis, 2017/01/25 22:33:25]

Is the = nullptr even necessary? I didn't think there were a lot of callsites.

[gab, 2017/02/13 19:57:00]

Guess not, made mandatory.

   ~MediaCodecLoop();
 
   // Optionally set the tick clock used for testing.  It is our caller's