possibly fix [2265804] OpenGL GLSurfaceView apps don't draw status bar drop shadow correctly

request a layout when asking the transparent region to be recomputed, without this
it may never happen, since the transparent region is only calculated during layout.

this also fixes an issue where some fullscreen apps will run slower than expected
because their transparent region is never processed.

Change-Id: Iba187ef7b23f08ad3454aaa6707a3d262551e30c