chromeos: Add external brightness control to chrome://flags.

Make --ash-enable-brightness-control settable via
chrome://flags to permit testing of DDC/CI-based brightness
adjustments of external displays in powerd.

Also add a bit of code to ensure that even if powerd
announces a brightness change via D-Bus, Chrome never
displays a bubble if there's no internal display connected.

BUG=315371

Review URL: https://codereview.chromium.org/191973004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256176 0039d316-1c4b-4281-b951-d872f2087c98
Fix URL truncation in ombnibox for Aura.

Truncate the match and description parts in the omnibox result view so
to maximize the amount of useful information for the user.

BUG=246837

Review URL: https://codereview.chromium.org/170293004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256177 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256177
Remove PlatformFile from safe browsing.

BUG=322664
R=mattm@chromium.org

Review URL: https://codereview.chromium.org/180213009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256178 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256178