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

ios/web/web_state/web_view_internal_creation_util.mm

Index: ios/web/web_state/web_view_internal_creation_util.mm
diff --git a/ios/web/web_state/web_view_internal_creation_util.mm b/ios/web/web_state/web_view_internal_creation_util.mm
index 5095110ff5225cd65dde288949e61442d8614181..c0f6142edf51097bf6adc2e02f443fd56c7e14b4 100644
--- a/ios/web/web_state/web_view_internal_creation_util.mm
+++ b/ios/web/web_state/web_view_internal_creation_util.mm
@@ -7,12 +7,15 @@
 #import <objc/runtime.h>
 
 #include "base/logging.h"
-#import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/web/public/web_client.h"
 #import "ios/web/web_state/ui/crw_context_menu_controller.h"
 #import "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 namespace {
@@ -60,17 +63,17 @@ WKWebView* BuildWKWebView(CGRect frame,
   web_view.allowsLinkPreview = NO;
 
   if (context_menu_delegate) {
-    base::scoped_nsobject<CRWContextMenuController> context_menu_controller(
-        [[CRWContextMenuController alloc]
-               initWithWebView:web_view
-            injectionEvaluator:nil
-                      delegate:context_menu_delegate]);
-    objc_setAssociatedObject(web_view, context_menu_controller.get(),
-                             context_menu_controller.get(),
+    CRWContextMenuController* context_menu_controller = [
+        [CRWContextMenuController alloc] initWithWebView:web_view
+                                      injectionEvaluator:nil
+                                                delegate:context_menu_delegate];
+    void* associated_object_key = (__bridge void*)context_menu_controller;
+    objc_setAssociatedObject(web_view, associated_object_key,
+                             context_menu_controller,
                              OBJC_ASSOCIATION_RETAIN_NONATOMIC);
   }
 
-  return [web_view autorelease];
+  return web_view;
 }
 
 WKWebView* BuildWKWebView(CGRect frame,