Move skia related files from content/common/gpu/client to gpu/skia_bindings.

gpu/skia_bindings/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 source_set("skia_bindings") {
   sources = [
     "gl_bindings_skia_cmd_buffer.cc",
     "gl_bindings_skia_cmd_buffer.h",
+    "grcontext_for_gles2_interface.cc",
+    "grcontext_for_gles2_interface.h",
   ]
   deps = [
     "//base",
     "//gpu/command_buffer/client:gles2_interface",
     "//skia",
   ]
 }