Create abstract interface for media::Pipeline.

media/base/media_log.cc

Index: media/base/media_log.cc
diff --git a/media/base/media_log.cc b/media/base/media_log.cc
index 916021a3a6340fe4a28bf30cbd492cef78c7492d..ed43742f307c5297f2f2e498d7e03ddcfabaa3f8 100644
--- a/media/base/media_log.cc
+++ b/media/base/media_log.cc
@@ -195,10 +195,11 @@ scoped_ptr<MediaLogEvent> MediaLog::CreateSeekEvent(float seconds) {
 }
 
 scoped_ptr<MediaLogEvent> MediaLog::CreatePipelineStateChangedEvent(
-    Pipeline::State state) {
+    PipelineImpl::State state) {
   scoped_ptr<MediaLogEvent> event(
       CreateEvent(MediaLogEvent::PIPELINE_STATE_CHANGED));
-  event->params.SetString("pipeline_state", Pipeline::GetStateString(state));
+  event->params.SetString("pipeline_state",
+                          PipelineImpl::GetStateString(state));
   return event;
 }