MacViews: support Views device permission prompt

chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm

Index: chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm
diff --git a/chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm b/chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm
index c38fa70d03fcd1d8a7c1b8e7903aa75ec5211954..852fbba7969c8be8e7451cd09e513bb0895e0e97 100644
--- a/chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.mm
@@ -9,6 +9,7 @@
 #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"
@@ -56,6 +57,8 @@ void DevicePermissionsDialogController::OnConstrainedWindowClosed(
 }
 
 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) {