SurfaceTexture: add the abandon method.

This change adds the 'abandon' method to the SurfaceTexture C++ class.
This method may be used to put the SurfaceTexture in an abandoned state,
causing all ISurfaceTexture methods to fail.

Change-Id: Ibd261f7b73f44e2bec36a8508bf92113cfb7cf95
diff --git a/include/gui/ISurfaceTexture.h b/include/gui/ISurfaceTexture.h
index 405a25a..1eda646 100644
--- a/include/gui/ISurfaceTexture.h
+++ b/include/gui/ISurfaceTexture.h
@@ -51,7 +51,7 @@
     // the given slot index, and the client is expected to mirror the
     // slot->buffer mapping so that it's not necessary to transfer a
     // GraphicBuffer for every dequeue operation.
-    virtual sp<GraphicBuffer> requestBuffer(int slot) = 0;
+    virtual status_t requestBuffer(int slot, sp<GraphicBuffer>* buf) = 0;
 
     // setBufferCount sets the number of buffer slots available. Calling this
     // will also cause all buffer slots to be emptied. The caller should empty