Switch base::Value typemapping to be by value instead of by unique_ptr.

content/renderer/media/video_capture_impl.cc

Index: content/renderer/media/video_capture_impl.cc
diff --git a/content/renderer/media/video_capture_impl.cc b/content/renderer/media/video_capture_impl.cc
index 4650bbbbf8b08687c031392239d137a9c940da52..67ea3e0afbb594dec29e70188e769290f7025a66 100644
--- a/content/renderer/media/video_capture_impl.cc
+++ b/content/renderer/media/video_capture_impl.cc
@@ -284,7 +284,7 @@ void VideoCaptureImpl::OnBufferReady(int32_t buffer_id,
 
   base::TimeTicks reference_time;
   media::VideoFrameMetadata frame_metadata;
-  frame_metadata.MergeInternalValuesFrom(*info->metadata);
+  frame_metadata.MergeInternalValuesFrom(info->metadata);
   const bool success = frame_metadata.GetTimeTicks(
       media::VideoFrameMetadata::REFERENCE_TIME, &reference_time);
   DCHECK(success);
@@ -329,7 +329,7 @@ void VideoCaptureImpl::OnBufferReady(int32_t buffer_id,
       base::Bind(&VideoCaptureImpl::DidFinishConsumingFrame, frame->metadata(),
                  buffer_finished_callback));
 
-  frame->metadata()->MergeInternalValuesFrom(*info->metadata);
+  frame->metadata()->MergeInternalValuesFrom(info->metadata);
 
   // TODO(qiangchen): Dive into the full code path to let frame metadata hold
   // reference time rather than using an extra parameter.