Initial version of external_oes texture support and unit test

Committed: https://skia.googlesource.com/skia/+/27a048700778d4cebfc23301d1780649791b0e03

Review URL: https://codereview.chromium.org/1451683002
diff --git a/include/gpu/gl/GrGLInterface.h b/include/gpu/gl/GrGLInterface.h
index ec27ace..31429a8 100644
--- a/include/gpu/gl/GrGLInterface.h
+++ b/include/gpu/gl/GrGLInterface.h
@@ -498,8 +498,8 @@
         GLPtr<GrGLObjectLabelProc> fObjectLabel;
 
         /* EGL functions */
-        GLPtr<GrEGLCreateImageProc> fCreateImage;
-        GLPtr<GrEGLDestroyImageProc> fDestroyImage;
+        GLPtr<GrEGLCreateImageProc> fEGLCreateImage;
+        GLPtr<GrEGLDestroyImageProc> fEGLDestroyImage;
     } fFunctions;
 
     // Per-GL func callback