Correct iOS build for latest Xcode beta.

ios/chrome/browser/infobars/infobar_controller.mm

 // Copyright 2013 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.
 
 #include "ios/chrome/browser/infobars/infobar_controller.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #import "ios/public/provider/chrome/browser/ui/infobar_view_protocol.h"
 
 @interface InfoBarController () {
   base::scoped_nsobject<UIView<InfoBarViewProtocol>> _infoBarView;
 }
 @end
 
 @implementation InfoBarController
 @synthesize delegate = _delegate;
 
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
 - (instancetype)initWithDelegate:(InfoBarViewDelegate*)delegate {
   self = [super init];
   if (self) {
     DCHECK(delegate);
     _delegate = delegate;
   }
   return self;
 }
 
 - (void)dealloc {
@@ skipping 30 matching lines @@
 - (void)removeView {
   [_infoBarView removeFromSuperview];
 }
 
 - (void)detachView {
   [_infoBarView resetDelegate];
   _delegate = nullptr;
 }
 
 @end