Return the transform to apply in getLastQueuedBuffer

Bug: 28428955
Change-Id: Id48f7d3bf3f5deb074cf0a6a52a41caac875db41
diff --git a/include/gui/GLConsumer.h b/include/gui/GLConsumer.h
index 8de3302..6267625 100644
--- a/include/gui/GLConsumer.h
+++ b/include/gui/GLConsumer.h
@@ -132,6 +132,12 @@
     // functions.
     void getTransformMatrix(float mtx[16]);
 
+    // Computes the transform matrix documented by getTransformMatrix
+    // from the BufferItem sub parts.
+    static void computeTransformMatrix(float outTransform[16],
+            const sp<GraphicBuffer>& buf, const Rect& cropRect,
+            uint32_t transform, bool filtering);
+
     // getTimestamp retrieves the timestamp associated with the texture image
     // set by the most recent call to updateTexImage.
     //