Convert MediaLog from being ref counted to owned by WebMediaPlayer.

media/blink/multibuffer_data_source_unittest.cc

Index: media/blink/multibuffer_data_source_unittest.cc
diff --git a/media/blink/multibuffer_data_source_unittest.cc b/media/blink/multibuffer_data_source_unittest.cc
index 0b5a1bafdc408b96040bb56f3e5717875e6ddd9d..90a6cea7ae16d287639939a6b6d0434a321cf5aa 100644
--- a/media/blink/multibuffer_data_source_unittest.cc
+++ b/media/blink/multibuffer_data_source_unittest.cc
@@ -195,7 +195,7 @@ class MockMultibufferDataSource : public MultibufferDataSource {
             task_runner,
             url_index,
             frame,
-            new media::MediaLog(),
+            &media_log_,
             host,
             base::Bind(&MockMultibufferDataSource::set_downloading,
                        base::Unretained(this))),
@@ -208,6 +208,7 @@ class MockMultibufferDataSource : public MultibufferDataSource {
  private:
   // Whether the resource is downloading or deferred.
   bool downloading_;
+  MediaLog media_log_;
 
   DISALLOW_COPY_AND_ASSIGN(MockMultibufferDataSource);
 };