MacViews: support Views device permission prompt

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/threading/thread_task_runner_handle.h"
 #include "chrome/browser/extensions/api/chrome_device_permissions_prompt.h"
+#include "chrome/browser/ui/browser_dialogs.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_window.h"
 #import "chrome/browser/ui/cocoa/extensions/device_permissions_view_controller.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
 #include "device/usb/usb_device.h"
 
 using extensions::DevicePermissionsPrompt;
 
 DevicePermissionsDialogController::DevicePermissionsDialogController(
     content::WebContents* web_contents,
@@ skipping 27 matching lines @@
   [view_controller_ devicesChanged];
 }
 
 void DevicePermissionsDialogController::OnConstrainedWindowClosed(
     ConstrainedWindowMac* window) {
   prompt_->Dismissed();
   base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
 }
 
 void ChromeDevicePermissionsPrompt::ShowDialog() {
+  if (chrome::ToolkitViewsWebUIDialogsEnabled())
+    return ChromeDevicePermissionsPrompt::ShowDialogViews();

[tapted, 2016/05/18 00:14:52]

I can't decide whether this is cool or sneaky :). C++ lets you return a "void"
value from a void function, but it usually just gets exploited in templated
code. Nothing really wrong with it I guess - just a bit obscure.  (also this
line could just be `return ShowDialogViews();` - the method isn't static - but
in some ways it's a nice indication that the call isn't to code that's "nearby",
so this is fine too).

   web_modal::WebContentsModalDialogManager* manager =
       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()));
   }
 }