Implement main blink target in GN.

Source/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.
 
 import("config.gni")
 if (is_clang) {
   import("//build/config/clang/clang.gni")
 }
 
+visibility = "//third_party/WebKit/*"
+
 # features ---------------------------------------------------------------------
 
 config("features") {
   defines = feature_defines_list
 }
 
 # inside_blink -----------------------------------------------------------------
 
 config("inside_blink") {
   defines = [
@@ skipping 51 matching lines @@
 
 # The follow configs apply to all targets except for unit tests, which rely on
 # static initializers.
 config("non_test_config") {
   cflags = []
 
   if (is_clang) {
     cflags += [ "-Wglobal-constructors" ]
   }
 }
-
-# stubs ------------------------------------------------------------------------
-
-# These set up include paths for targets that haven't been converted yet. They
-# can be removed when the corresponding targets have been converted to GN.
-config("npapi_stub") {
-  include_dirs = [ "//third_party/npapi", "//third_party/npapi/bindings" ]
-}