[WebModals] New API for browser-scoped popup management.

apps/app_window.cc

Index: apps/app_window.cc
diff --git a/apps/app_window.cc b/apps/app_window.cc
index e2d837d4e3847cda39e2cf9954fccc150f5931b4..db1f54399664886a0bbc753be79565fe9b04cfbc 100644
--- a/apps/app_window.cc
+++ b/apps/app_window.cc
@@ -264,6 +264,7 @@ void AppWindow::Init(const GURL& url,
     content::WebContentsObserver::Observe(web_contents);
   }
   delegate_->InitWebContents(web_contents);
+
   WebContentsModalDialogManager::CreateForWebContents(web_contents);
   // TODO(jamescook): Delegate out this creation.
   extensions::ChromeExtensionWebContentsObserver::CreateForWebContents(
@@ -286,6 +287,10 @@ void AppWindow::Init(const GURL& url,
 
   native_app_window_.reset(delegate_->CreateNativeAppWindow(this, new_params));
 
+  popup_manager_.reset(
+      new web_modal::PopupManager(GetWebContentsModalDialogHost()));
+  popup_manager_->RegisterWith(web_contents);
+
   // Prevent the browser process from shutting down while this window exists.
   AppsClient::Get()->IncrementKeepAliveCount();
   UpdateExtensionAppIcon();