Remove include/gpu/gl from include paths.

This path is not used as an include path by public.bzl nor by Chromium.
Remove this include path to avoid breaking these clients and generally
make these includes more specific.

Change-Id: I9391d38d5241870086bf47cb8e49146736dc4ded
Reviewed-on: https://skia-review.googlesource.com/129561
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

BUILD.gn

@@ -109,7 +109,6 @@ skia_public_includes = [
   "include/effects",
   "include/encode",
   "include/gpu",
-  "include/gpu/gl",
   "include/atlastext",
   "include/pathops",
   "include/ports",

tools/sk_app/win/GLWindowContext_win.cpp

@@ -9,7 +9,7 @@
 #include <Windows.h>
 #include <GL/gl.h>
 #include "../GLWindowContext.h"
-#include "GrGLInterface.h"
+#include "gl/GrGLInterface.h"
 #include "WindowContextFactory_win.h"
 #include "win/SkWGL.h"