Round the task thumbnail corners as per the mocks by setting the bitmap
as a shader.
Bug: 114136250
Test: See rounded thumbnails on recents Go
Change-Id: I2bf8ebce34deb0d1cb6199cf8f6d5fa6ac746bb8
This CL adds a drawable for the default thumbnail view and
refactors the logic to get the default icon/thumbnail/label if
null to separate methods for re-use in later CLs.
Bug: 114136250
Test: Manual; Go to icon recents
Change-Id: I511ea40ace040fc53ffc69c27149f24d69bda7b0
(cherry picked from commit 34ee30c4f9)
Kevin