Remove string.h from SkTypes.h

Change-Id: I2be84f37ea11a386206a96d2fef6e0fc9464e21b
Reviewed-on: https://skia-review.googlesource.com/135264
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/include/gpu/gl/GrGLFunctions.h b/include/gpu/gl/GrGLFunctions.h
index af1b9f7..e0bc390 100644
--- a/include/gpu/gl/GrGLFunctions.h
+++ b/include/gpu/gl/GrGLFunctions.h
@@ -12,6 +12,8 @@
 #include "GrGLTypes.h"
 #include "../private/SkTLogic.h"
 
+#include <cstring>
+
 extern "C" {
 
 ///////////////////////////////////////////////////////////////////////////////