[Extensions] Rejigger the NTP overriden bubble for multiple platforms
When an extension overrides the NTP, we show a bubble to the user saying
"Is this the new tab page you were expecting?". Currently, this bubble
is only shown on Windows. However, we'd like to bring it over to other
platforms (CrOS and MacOS). This is slightly complicated because we
don't want to prompt users about extensions they've already installed.
Rejigger the bubble logic to:
- Add the ability to perform a one-time acknowledgement of
ntp-overriding extensions, which will be used when introducing the NTP to
new platforms.
- Allow the bubble to be shown on platforms other than Windows.
Add testing for the acknowledgment and the bubble's appearance on all
platforms.
Note: this CL does *not* enable the bubble on any other platforms. It only
sets it up so that a follow-up CL can flip the switch.
BUG=695283
Review-Url: https://codereview.chromium.org/2901053002
Cr-Commit-Position: refs/heads/master@{#475920}
9 files changed
