[ObjC ARC] Converts ios/web:web to ARC.

ios/web/web_state/ui/wk_web_view_configuration_provider.mm

 // 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 "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
 
 #import <Foundation/Foundation.h>
 #import <WebKit/WebKit.h>
 
 #import "base/ios/weak_nsobject.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "ios/web/public/browser_state.h"
 #import "ios/web/web_state/js/page_script_util.h"
 #import "ios/web/web_state/ui/crw_wk_script_message_router.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 namespace {
 // A key used to associate a WKWebViewConfigurationProvider with a BrowserState.
 const char kWKWebViewConfigProviderKeyName[] = "wk_web_view_config_provider";
 
 // Returns an autoreleased instance of WKUserScript to be added to
 // configuration's userContentController.
 WKUserScript* InternalGetEarlyPageScript(BrowserState* browser_state) {
-  return [[[WKUserScript alloc]
+  return [[WKUserScript alloc]
         initWithSource:GetEarlyPageScript(browser_state)
          injectionTime:WKUserScriptInjectionTimeAtDocumentStart
-      forMainFrameOnly:YES] autorelease];
+      forMainFrameOnly:YES];
 }
 
 }  // namespace
 
 // static
 WKWebViewConfigurationProvider&
 WKWebViewConfigurationProvider::FromBrowserState(BrowserState* browser_state) {
   DCHECK([NSThread isMainThread]);
   DCHECK(browser_state);
   if (!browser_state->GetUserData(kWKWebViewConfigProviderKeyName)) {
@@ skipping 23 matching lines @@
     }
     // API available on iOS 9, although doesn't appear to enable inline playback
     // Works as intended on iOS 10+
     [configuration_ setAllowsInlineMediaPlayback:YES];
     // setJavaScriptCanOpenWindowsAutomatically is required to support popups.
     [[configuration_ preferences] setJavaScriptCanOpenWindowsAutomatically:YES];
     [[configuration_ userContentController]
         addUserScript:InternalGetEarlyPageScript(browser_state_)];
   }
   // Prevent callers from changing the internals of configuration.
-  return [[configuration_ copy] autorelease];
+  return [configuration_ copy];
 }
 
 CRWWKScriptMessageRouter*
 WKWebViewConfigurationProvider::GetScriptMessageRouter() {
   DCHECK([NSThread isMainThread]);
   if (!router_) {
     WKUserContentController* userContentController =
         [GetWebViewConfiguration() userContentController];
     router_.reset([[CRWWKScriptMessageRouter alloc]
         initWithUserContentController:userContentController]);
   }
   return router_;
 }
 
 void WKWebViewConfigurationProvider::Purge() {
   DCHECK([NSThread isMainThread]);
 #if DCHECK_IS_ON()
-  base::WeakNSObject<id> weak_configuration(configuration_);
-  base::WeakNSObject<id> weak_router(router_);
-  base::WeakNSObject<id> weak_process_pool([configuration_ processPool]);
+  base::WeakNSObject<id> weak_configuration;
+  base::WeakNSObject<id> weak_router;
+  // It's expected that the weak objects auto-nil by the end of this method.
+  // They should not be in any autoreleasepool that might keep them alive.
+  @autoreleasepool {
+    weak_configuration.reset(configuration_);
+    weak_router.reset(router_);
+  }
+// TODO(crbug.com/522672): See commented out DCHECK below.
+// __weak id weak_process_pool = [configuration_ processPool];
 #endif  // DCHECK_IS_ON()
   configuration_.reset();
   router_.reset();
   // Make sure that no one retains configuration, router, processPool.
 #if DCHECK_IS_ON()
   DCHECK(!weak_configuration);
   DCHECK(!weak_router);
   // TODO(crbug.com/522672): Enable this DCHECK.
   // DCHECK(!weak_process_pool);
 #endif  // DCHECK_IS_ON()
 }
 
 }  // namespace web