Add BluetoothDevice::PairingDelegate::AuthorizePairing

Now that we have the concept of a default pairing agent that may be
used to handle incoming pairing requests we need to handle the case
of authorizing a Just-Works pairing request from an unknown device.

BUG=329583
TEST=device_unittests included

Review URL: https://codereview.chromium.org/168603006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253919 0039d316-1c4b-4281-b951-d872f2087c98
Makes it clear in unittests that the system is missing some of fonts.

Added some error messages to FontTest.GetActualFontNameForTesting.

BUG=347429
TEST=Run ui_unittests.

Review URL: https://codereview.chromium.org/182873002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253920 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253919
SVN changes up to revision 253920