[iOS/GN] Fix the extension used by application extension bundles.

build/config/ios/rules.gni

 # Copyright 2015 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/config/mac/base_rules.gni")
 
 # Generates Info.plist files for Mac apps and frameworks.
 #
 # Arguments
 #
@@ skipping 212 matching lines @@
 #   extra_substitutions:
 #       (optional) list of string in "key=value" format, each value will
 #       be used as an additional variable substitution rule when generating
 #       the application Info.plist
 #
 #   info_plist:
 #       path to the template to use to generate the application Info.plist
 #       by performing variable substitutions.
 #
 # For more information, see "gn help executable".
-template("ios_appext_bundle") {
+template("ios_appex_bundle") {
   ios_app_bundle(target_name) {
     forward_variables_from(invoker,
                            "*",
                            [
                              "bundle_extension",
                              "product_type",
                            ])
-    bundle_extension = ".appext"
+    bundle_extension = ".appex"
     product_type = "com.apple.product-type.app-extension"
 
     # Add linker flags required for an application extension (determined by
     # inspecting the link command-line when using Xcode 9.0+).
     if (!defined(ldflags)) {
       ldflags = []
     }
     ldflags += [
       "-e",
       "_NSExtensionMain",
@@ skipping 241 matching lines @@
                              [
                                "testonly",
                                "visibility",
                              ])
       public_deps = [
         ":$_framework_target+link",
       ]
     }
   }
 }