Add glCopyTexSubImage2D to GrGLInterface

Author: bsalomon@google.com

Reviewed By: robertphillips@google.com

Review URL: https://chromiumcodereview.appspot.com/13941006

git-svn-id: http://skia.googlecode.com/svn/trunk@8634 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLCreateNullInterface.cpp b/src/gpu/gl/GrGLCreateNullInterface.cpp
index ebaacbc..5a5ec6b 100644
--- a/src/gpu/gl/GrGLCreateNullInterface.cpp
+++ b/src/gpu/gl/GrGLCreateNullInterface.cpp
@@ -179,6 +179,7 @@
         interface->fColorMask = noOpGLColorMask;
         interface->fCompileShader = noOpGLCompileShader;
         interface->fCompressedTexImage2D = noOpGLCompressedTexImage2D;
+        interface->fCopyTexSubImage2D = noOpGLCopyTexSubImage2D;
         interface->fCreateProgram = nullGLCreateProgram;
         interface->fCreateShader = nullGLCreateShader;
         interface->fCullFace = noOpGLCullFace;