The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fa42e413dc97ce4adbd2b398198f7e350623d8f7

commit fa42e413dc97ce4adbd2b398198f7e350623d8f7
Author: Daniel Cheng <dcheng@chromium.org>
Date: Tue Jul 18 04:06:44 2017

Don't pass ownership of MediaEngagementScore by raw pointer.

As this object isn't passed around very much, just make it movable. The
majority of the time, RVO applies and there is no move anyway.

Also make some string constants actually constant.

Bug:  741626 
Change-Id: If505ceda66b2cd1c5892ecc35448d90fccdaa829
Reviewed-on: https://chromium-review.googlesource.com/571625
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487380}
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_contents_observer_unittest.cc
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_score.cc
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_score.h
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_service.cc
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_service.h
[modify] https://crrev.com/fa42e413dc97ce4adbd2b398198f7e350623d8f7/chrome/browser/media/media_engagement_service_unittest.cc