Window: Add query for consumer usage bits.

Bug: 9592202
Change-Id: Ied2fdb985dc59dd9c0f26c515353abdc37f0eb77
diff --git a/include/system/window.h b/include/system/window.h
index b8a19c8..7ce59e0 100644
--- a/include/system/window.h
+++ b/include/system/window.h
@@ -230,7 +230,13 @@
      * Boolean that indicates whether the consumer is running more than
      * one buffer behind the producer.
      */
-    NATIVE_WINDOW_CONSUMER_RUNNING_BEHIND = 9
+    NATIVE_WINDOW_CONSUMER_RUNNING_BEHIND = 9,
+
+    /*
+     * The consumer gralloc usage bits currently set by the consumer.
+     * The values are defined in hardware/libhardware/include/gralloc.h.
+     */
+    NATIVE_WINDOW_CONSUMER_USAGE_BITS = 10
 };
 
 /* Valid operations for the (*perform)() hook.