Remove CWV class and move setting User Agent to CWVWebViewConfiguration.

ios/web_view/BUILD.gn

 # Copyright 2016 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/ios/ios_sdk.gni")
 import("//build/config/ios/rules.gni")
 import("//tools/grit/repack.gni")
 
 config("config") {
   defines = [ "CWV_IMPLEMENTATION" ]
   libs = [
     "CoreGraphics.framework",
     "Foundation.framework",
     "MobileCoreServices.framework",
     "UIKit.framework",
   ]
 }
 
 ios_framework_bundle("web_view") {
   output_name = "ChromeWebView"
   info_plist = "Info.plist"
 
   public_headers = [
     "public/ChromeWebView.h",
-    "public/cwv.h",
     "public/cwv_export.h",
     "public/cwv_html_element.h",
     "public/cwv_navigation_action.h",
     "public/cwv_navigation_delegate.h",
     "public/cwv_translate_delegate.h",
     "public/cwv_translate_manager.h",
     "public/cwv_ui_delegate.h",
     "public/cwv_user_content_controller.h",
     "public/cwv_user_script.h",
     "public/cwv_web_view.h",
     "public/cwv_web_view_configuration.h",
   ]
 
   public = [
     "public/ChromeWebView.h",
   ]
 
   sources = [
-    "internal/cwv.mm",
     "internal/cwv_html_element.mm",
     "internal/cwv_html_element_internal.h",
     "internal/cwv_navigation_action.mm",
     "internal/cwv_navigation_action_internal.h",
     "internal/cwv_user_content_controller.mm",
     "internal/cwv_user_content_controller_internal.h",
     "internal/cwv_user_script.mm",
     "internal/cwv_web_view.mm",
     "internal/cwv_web_view_configuration.mm",
     "internal/cwv_web_view_configuration_internal.h",
@@ skipping 77 matching lines @@
   public_deps = [
     ":repack_resources",
   ]
   sources = [
     "$target_gen_dir/web_view_resources.pak",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }