Make keyboard aware of input type


This CL introduces inputType and inputTypeToLayoutMap attributes to kb-keyboard.
It should be able to support load different keyboard layout based on the type of
current input box in general.

As a first step, we only add support for numeric keyboard layout for number input
box in this CL (webui keyboard only).

BUG=290325

Review URL: https://chromiumcodereview.appspot.com/23522033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224713 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224713