GitLab

```yaml
IN CASE OF PROBLEMS: If this CL causes your site/app to break, you are
using deprecated features that have now been removed. Please see [2] to
enroll in the Deprecation Extension program to give yourself more time.
```

With this CL, two of the three Web Components v0 APIs are disabled by
default. The third, HTML Imports, will be disabled (soon) by a separate CL.

These features were deprecated in August, 2018, in [1]. The original
removal timeline called for a deadline of M73. Due to high use counters
for the features, this deadline was extended to M80, which is now here.
For those sites that need additional time, there is a "deprecation
extension" (sometimes called a "reverse origin trial") that can be used
to extend this removal for specific sites through M87. For more
information on that, see [2]. For overall context on this removal,
including motivation and ways to test/upgrade, see [3].

With this CL, these features will still be enabled for testing across
all test suites. Once this CL has had a chance to land and stabilize,
subsequent CLs will disable the features for all tests by default, and
enable a virtual test suite to continue testing specific code with WCv0
features enabled, to ensure the features continue to function through
the end of the deprecation extension period.

[1] https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/h-JwMiPUnuU/sl79aLoLBQAJ
[2] https://developers.chrome.com/origintrials/#/view_trial/2431943798780067841
[3] https://developers.google.com/web/updates/2019/07/web-components-time-to-upgrade

Bug: 911943
Change-Id: I939e1ead03a3196e63f0f9c192f916c87ab16562
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1850795Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: Darin Fisher <darin@chromium.org>
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708031}