GitLab

Make the PluginProxy follow the standard BrowserProxy pattern (i.e.
define an interface and implement separately), and use
addSingletonGetter(). This allows for better type coverage when using
the stub in tests.

Add closure compilation for:
header_test
invalid_settings_browsertest
test_plugin_proxy (renamed from plugin_stub)

Bug: 1000989
Change-Id: I6e0cf064a6789b2cdc87b617fd0fdd58d5039f48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2317165
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792025}