fix circular dependency libnativewindow <-> libui

Bug: 37647680
Bug: 37648355
Test: compile, manual
Change-Id: I9631beea52e23ebb519411f943c6f5062aedd2e5
diff --git a/include/gui/Surface.h b/include/gui/Surface.h
index 8b1d106..c8c6e99 100644
--- a/include/gui/Surface.h
+++ b/include/gui/Surface.h
@@ -27,7 +27,7 @@
 #include <utils/Mutex.h>
 #include <utils/RefBase.h>
 
-struct ANativeWindow_Buffer;
+#include <system/window.h>
 
 namespace android {