Refactor SurfaceTexture a bit.

Rearranges updateTexImage() so that the SurfaceFlinger-specific
behavior is in a new SurfaceFlingerConsumer subclass.

SurfaceTexture behavior should not be altered.  Instead of
acquire-bind-release we now do acquire-release-bind, but since
it's all done with the lock held there shouldn't be any
externally-visible change.

Change-Id: Ia566e4727945e2cfb9359fc6d2a8f8af64d7b7b7
diff --git a/services/surfaceflinger/Android.mk b/services/surfaceflinger/Android.mk
index 329bbd5..f7870f4 100644
--- a/services/surfaceflinger/Android.mk
+++ b/services/surfaceflinger/Android.mk
@@ -17,6 +17,7 @@
     GLExtensions.cpp                        \
     MessageQueue.cpp                        \
     SurfaceFlinger.cpp                      \
+    SurfaceFlingerConsumer.cpp              \
     SurfaceTextureLayer.cpp                 \
     Transform.cpp                           \