Add new app banner metrics using InstallableStatusCode.
The InstallableManager reports status codes to signal if the checking
pipeline failed in some way. This CL introduces a new UMA metric to
report the value of this code, and introduces new codes to ensure that
every run through the banner pipeline results in precisely one code.
This new metric is intended to be the final source of truth for banners.
Additional testing is added to ensure the correct histogram values are
recorded. The existing metrics will be removed in a future CL.
BUG=628921
Review-Url: https://codereview.chromium.org/2178833002
Cr-Commit-Position: refs/heads/master@{#412143}
18 files changed
