Clean up warnings in EGL.

Bug: http://b/26936282
Change-Id: I059628332d638f080a5236eed62cf0afa1d4d6ba
diff --git a/opengl/libs/EGL/egl_object.h b/opengl/libs/EGL/egl_object.h
index f5a9f58..17a8304 100644
--- a/opengl/libs/EGL/egl_object.h
+++ b/opengl/libs/EGL/egl_object.h
@@ -37,7 +37,7 @@
 namespace android {
 // ----------------------------------------------------------------------------
 
-struct egl_display_t;
+class egl_display_t;
 
 class egl_object_t {
     egl_display_t *display;