Add support for EGLImage to GrGLInterface

BUG=skia:

Review URL: https://codereview.chromium.org/1434813002
diff --git a/src/gpu/gl/SkNullGLContext.cpp b/src/gpu/gl/SkNullGLContext.cpp
index 877eed9..e2a80ce 100644
--- a/src/gpu/gl/SkNullGLContext.cpp
+++ b/src/gpu/gl/SkNullGLContext.cpp
@@ -491,7 +491,7 @@
     functions->fBindFragDataLocationIndexed = noOpGLBindFragDataLocationIndexed;
 
     interface->fExtensions.init(kGL_GrGLStandard, functions->fGetString, functions->fGetStringi,
-                                functions->fGetIntegerv);
+                                functions->fGetIntegerv, nullptr, GR_EGL_NO_DISPLAY);
     return interface;
 }