Change window type of Media Projection dialog

With the dialog changes of not closing QS, the dialog type needs to
change to present on top of the shade.

This CL changes it to match that of the dialog launched by CastTile.

Fixes: 209532003
Test: manual
(cherry picked from commit c5bd5733)
(cherry picked from commit 467b282e)
Merged-In: I937678a5d8ee91902c324aa063e48610de7b0f74
Change-Id: I937678a5d8ee91902c324aa063e48610de7b0f74