ChromeFeaturesServiceProvider reports whether PluginVm is allowed

Based on: https://chromium-review.googlesource.com/c/chromium/src/+/1607641
This extends plugin_vm::IsPluginVmAllowedForProfile with an
alternative condition for testing and adds the whole check to
ChromeFeaturesServiceProvider so that Chrome OS does the proper
checks for PluginVm.

Adapts all relevant PluginVm tests accordingly.
Currently only PluginVm unit tests rely on PluginVmTestHelper - plan to
change it in the future CLs and file a P3 bug for now.

--gtest_filter="PluginVm*"

Bug: 920999
Test: unit_tests --gtest_filter="PluginVm*" && browser_tests
Change-Id: I0e24186fbf4411de423141dfbf33bf2886b2a357
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1624192
Commit-Queue: Olya Kalitova <okalitova@chromium.org>
Reviewed-by: Alex Oldemeier <aoldemeier@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662596}
7 files changed