Enable AutoResize for Constrained Web Dialogs for Mac.

chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.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 "chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
@@ skipping 15 matching lines @@
                                                            prompt:prompt]);
 
   prompt_->SetObserver(this);
 
   base::scoped_nsobject<NSWindow> window([[ConstrainedWindowCustomWindow alloc]
       initWithContentRect:[[view_controller_ view] bounds]]);
   [[window contentView] addSubview:[view_controller_ view]];
 
   base::scoped_nsobject<CustomConstrainedWindowSheet> sheet(
       [[CustomConstrainedWindowSheet alloc] initWithCustomWindow:window]);
-  constrained_window_.reset(
-      new ConstrainedWindowMac(this, web_contents, sheet));
+  constrained_window_.reset(ShowWebModalDialogMac(this, web_contents, sheet));
 }
 
 DevicePermissionsDialogController::~DevicePermissionsDialogController() {
   prompt_->SetObserver(nullptr);
 }
 
 void DevicePermissionsDialogController::Dismissed() {
   constrained_window_->CloseWebContentsModalDialog();
 }
 
@@ skipping 12 matching lines @@
       web_modal::WebContentsModalDialogManager::FromWebContents(web_contents());
   if (manager) {
     // These objects will delete themselves when the dialog closes.
     new DevicePermissionsDialogController(web_contents(), prompt());
   } else {
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE,
         base::Bind(&DevicePermissionsPrompt::Prompt::Dismissed, prompt()));
   }
 }