DevTools: introduce Browser.grantPermissions

This patch adds permission management over DevTools protocol:
- Browser.grantPermissions to grant permissions to origin
- Browser.resetPermissions to reset devtools permissions to defaults

Testing overview:
- content_shell's devtools manager delegate is updated to resolve the default
  browser context. This way functionality can be tested in layout_tests
- a new browser-grant-permissions.js test is added to test added methods
- geolocation test is rewritten to use protocol instead of PermissionsUtil layout_test hook
  to verify that protocol permissions work with geolocation overrides.

BUG=631464
R=dgozman

Change-Id: I6d9451339c319781c47c7db9db02c9cd08115c26
Reviewed-on: https://chromium-review.googlesource.com/1185877
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585630}
23 files changed