Select GL transport and draw call flush interval based on prop

bug: 140112486

Normally, different graphics methods would be communicated over the pipe
in the GL extension string, but if the transport medium itself is in
question, we need another method. Thus, we use Android's property_get
with the following property keys:

ro.kernel.qemu.gltransport # to control the transport type
ro.kernel.qemu.gltransport.drawFlushInterval # control draw call flush
interval

The default is to use goldfish pipe and have a flush interval of 800
draw calls.

Change-Id: Id1911e194d04f83379b576de01c93f7c2c680a4c
4 files changed