Fix ShortcutIntentBuilder to use LetterTileDrawables

Use LetterTileDrawables, instead of Bitmap drawables when generating
shortcut icons for contacts without a contact photo.

To do this, the methods generatePhoneNumberIcon() and
generateQuickContactIcon have to be modified to draw a drawable on
the canvas instead of a bitmap.

Bug: 13279862
Change-Id: Ife7bbca27a7d1b942c8a8ea908dd9896c5fe063a
(cherry picked from commit 30dd6e7e1a9279b91e9ee0ad36c34545c5b6c45a)