Create abstract interface for media::Pipeline.

media/base/media_log.h

Index: media/base/media_log.h
diff --git a/media/base/media_log.h b/media/base/media_log.h
index c547ef776db979abf028d6fbff9cca2a1d625861..fc70576654aab0fa1552bbafee37d9ae67e6ae9e 100644
--- a/media/base/media_log.h
+++ b/media/base/media_log.h
@@ -57,7 +57,7 @@ class MEDIA_EXPORT MediaLog : public base::RefCountedThreadSafe<MediaLog> {
   scoped_ptr<MediaLogEvent> CreateLoadEvent(const std::string& url);
   scoped_ptr<MediaLogEvent> CreateSeekEvent(float seconds);
   scoped_ptr<MediaLogEvent> CreatePipelineStateChangedEvent(
-      Pipeline::State state);
+      PipelineImpl::State state);
   scoped_ptr<MediaLogEvent> CreatePipelineErrorEvent(PipelineStatus error);
   scoped_ptr<MediaLogEvent> CreateVideoSizeSetEvent(
       size_t width, size_t height);