Added MediaSourceState unit test.

media/base/mock_filters.h

Index: media/base/mock_filters.h
diff --git a/media/base/mock_filters.h b/media/base/mock_filters.h
index 30a48eb52c31c535b5172e8a975e4932027933f0..0185567b84245bb33e088650047cf0e86f433312 100644
--- a/media/base/mock_filters.h
+++ b/media/base/mock_filters.h
@@ -24,6 +24,7 @@
 #include "media/base/pipeline_status.h"
 #include "media/base/renderer.h"
 #include "media/base/renderer_client.h"
+#include "media/base/stream_parser.h"
 #include "media/base/text_track.h"
 #include "media/base/text_track_config.h"
 #include "media/base/time_source.h"
@@ -375,6 +376,29 @@ class MockCdmContext : public CdmContext {
   DISALLOW_COPY_AND_ASSIGN(MockCdmContext);
 };
 
+class MockStreamParser : public StreamParser {
+ public:
+  MockStreamParser();
+  ~MockStreamParser() override;
+
+  // StreamParser interface
+  MOCK_METHOD8(
+      Init,
+      void(const InitCB& init_cb,
+           const NewConfigCB& config_cb,
+           const NewBuffersCB& new_buffers_cb,
+           bool ignore_text_track,
+           const EncryptedMediaInitDataCB& encrypted_media_init_data_cb,
+           const NewMediaSegmentCB& new_segment_cb,
+           const EndMediaSegmentCB& end_of_segment_cb,
+           const scoped_refptr<MediaLog>& media_log));
+  MOCK_METHOD0(Flush, void());
+  MOCK_METHOD2(Parse, bool(const uint8_t*, int));
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MockStreamParser);
+};
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_MOCK_FILTERS_H_