Graphical Optimizations
Graphical Optimizations

Enabled Backface culling, removed an unnecessary clearframebuffer
call, and replaced the main clearbuffer call with a call to
cleardepthbuffer.

These changes give us around a 25% increase of framerate on
the Nexus-6

Change-Id: I85225b868902cffd92b3288f8f9846fcd205db9e

google/zooshi,google/zooshi,google/zooshi,google/zooshi,google/zooshi