Annotates functions returning retained objects.

ios/web/web_state/web_view_internal_creation_util.mm

 // 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 "ios/web/web_state/web_view_internal_creation_util.h"
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ios/web/public/web_client.h"
 #import "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
@@ skipping 14 matching lines @@
       WKWebViewConfigurationProvider::FromBrowserState(browser_state);
   DCHECK_EQ([config_provider.GetWebViewConfiguration() processPool],
             [configuration processPool]);
 }
 
 }  // namespace
 
 WKWebView* CreateWKWebView(CGRect frame,
                            WKWebViewConfiguration* configuration,
                            BrowserState* browser_state,
-                           BOOL use_desktop_user_agent) {
+                           BOOL use_desktop_user_agent) NS_RETURNS_RETAINED {
   VerifyWKWebViewCreationPreConditions(browser_state, configuration);
 
   GetWebClient()->PreWebViewCreation();
   WKWebView* web_view =
       [[WKWebView alloc] initWithFrame:frame configuration:configuration];
 
   // Set the user agent.
   web_view.customUserAgent = base::SysUTF8ToNSString(
       web::GetWebClient()->GetUserAgent(use_desktop_user_agent));
 
   // By default the web view uses a very sluggish scroll speed. Set it to a more
   // reasonable value.
   web_view.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;
 
   // Starting in iOS10, |allowsLinkPreview| defaults to YES.  This should be
   // disabled since the default implementation will open the link in Safari.
   // TODO(crbug.com/622746): Remove once web// link preview implementation is
   // created.
   web_view.allowsLinkPreview = NO;
 
   return web_view;
 }
 
 WKWebView* CreateWKWebView(CGRect frame,
                            WKWebViewConfiguration* configuration,
-                           BrowserState* browser_state) {
+                           BrowserState* browser_state) NS_RETURNS_RETAINED {
   BOOL use_desktop_user_agent = NO;
   return CreateWKWebView(frame, configuration, browser_state,
                          use_desktop_user_agent);
 }
 
 }  // namespace web