Fix build.

Added missing #include <string.h>.

Change-Id: Idf151876851110098fe538a042f896784821919b
diff --git a/opengl/tests/gl_perf/filltest.cpp b/opengl/tests/gl_perf/filltest.cpp
index ef85807..3d5757f 100644
--- a/opengl/tests/gl_perf/filltest.cpp
+++ b/opengl/tests/gl_perf/filltest.cpp
@@ -19,6 +19,7 @@
 #include <time.h>
 #include <sched.h>
 #include <sys/resource.h>
+#include <string.h>
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>