Inline extensions .gypi files into GN build.

extensions/shell/common/api/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("//build/json_schema_api.gni")
 import("//tools/json_schema_compiler/json_features.gni")
-import("schemas.gni")
+
+schema_sources = [ "identity.idl" ]
+root_namespace = "extensions::shell::api::%(namespace)s"
 
 # GYP version: extensions/shell/common/api/api.gyp:shell_api
 json_schema_api("api") {
   sources = schema_sources
   schemas = true
   bundle = true
   bundle_name = "Shell"
 }
 
 # GYP version: extensions/shell/browser/api/api_registration.gyp:shell_api_registration
@@ skipping 42 matching lines @@
 }
 
 group("extensions_features") {
   public_deps = [
     ":shell_api_features",
     ":shell_behavior_features",
     ":shell_manifest_features",
     ":shell_permission_features",
   ]
 }