Default browser selection for Telemetry on Android

If no --browser switch is specified when running Telemetry tests for Android, we now
find the most recent local build and automatically update the .apk on the device if needed.

BUG=273233, 273232

Review URL: https://codereview.chromium.org/25094005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227411 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227411
FrameTree: comment typo fixes + one old weird unittest trick

BUG=245126

Review URL: https://codereview.chromium.org/25686009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227412 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227412