Add a temporary hack to report screen on while dozing.

The window manager and view hierarchy currently disable all drawing
when PowerManager.isScreenOn() returns false so no drawing occurs
while dozing.  This will be fixed in a future patch to take the
display blanking state into account correctly.

This patch is a workaround to unblock development in the meantime.

Bug: 13133142
Change-Id: I2dc0b422c77285e657d73adca2606aa68264d987