mozilla-b2g/gaia — pull request #8863 by rexboy7 (2013-03-28 04:32:42+00:00)
Title: Bug 830644 - [Keyboard][HIDPI] support high resolution devices

If you want to check with desktop build, apply
https://bugzilla.mozilla.org/attachment.cgi?id=728080
with
$ HIDPI=1 make
$ b2g --screen=480x800

(see comment 122 & comment 138 in the bug)