fix debug.sf.showbackground

Change-Id: Ie4eeca006ad6d8030900d8cb0029e4d1c22474fb
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 61d08aa..a6b1422 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1023,6 +1023,8 @@
             glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
         }
         glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+        glLoadIdentity();
+        glMatrixMode(GL_MODELVIEW);
     }
 }