media: Fix MergeMetadata function

We need to reindex the entries of metadata after merge metadata from
separated partial capture results.

BUG=b:137810394
TEST=Check if we use correct index to get meatadata from 2nd partial
result.

Change-Id: I960276452175423aa238616013841ccb265e820c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1735567Reviewed-by: Shik Chen <shik@chromium.org>
Commit-Queue: Hsu Wei-Cheng <mojahsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683925}

media/capture/video/chromeos/camera_metadata_utils.cc

@@ -121,6 +121,7 @@ void MergeMetadata(cros::mojom::CameraMetadataPtr* to,
     tags.insert(entry->tag);
     (*to)->entries->push_back(entry->Clone());
   }
+  SortCameraMetadata(to);
 }
 
 }  // namespace media