Add an option to make blink media logging verbose

We want HTMLMediaElement and MSE media logging to be always enabled on
Chromecast, since we are getting these logged into system logs and
use them to investigate bugs when we receive feedback reports from
users, so we want these logs to use VLOG and be present in our release
builds. We'll define VERBOSE_BLINK_MEDIA_LOGGING for Chromecast builds
only, so that other flavors of Chromium/Chrome are not affected by this
in any way.

Review-Url: https://codereview.chromium.org/2146203002
Cr-Commit-Position: refs/heads/master@{#406349}
3 files changed