cros: Enable WebUILoginView reuse.

chrome/browser/chromeos/login/ui/webui_login_view.h

Index: chrome/browser/chromeos/login/ui/webui_login_view.h
diff --git a/chrome/browser/chromeos/login/ui/webui_login_view.h b/chrome/browser/chromeos/login/ui/webui_login_view.h
index 5fbd2c7b2e62852ac114824ed3307ddcf2bc9b0d..79d77ab4da66fe3476554d7556384ea9588f5441 100644
--- a/chrome/browser/chromeos/login/ui/webui_login_view.h
+++ b/chrome/browser/chromeos/login/ui/webui_login_view.h
@@ -34,6 +34,7 @@ class Widget;
 namespace chromeos {
 
 class OobeUI;
+class SharedWebViewUsageHandle;
 
 // View used to render a WebUI supporting Widget. This widget is used for the
 // WebUI based start up and lock screens. It contains a WebView.
@@ -43,10 +44,15 @@ class WebUILoginView : public views::View,
                        public ChromeWebModalDialogManagerDelegate,
                        public web_modal::WebContentsModalDialogHost {
  public:
+  struct WebViewSettings {
+    // URL of the WebView to preload and reuse across WebUILoginView instances.
+    GURL preloaded_url;

[xiyuan, 2016/12/09 22:37:30]

nit: #include "url/gurl.h" and get rid of forward decl since we declare it as
member.

[jdufault, 2016/12/12 18:23:09]

Done.

+  };
+
   // Internal class name.
   static const char kViewClassName[];
 
-  WebUILoginView();
+  explicit WebUILoginView(const WebViewSettings& settings);
   ~WebUILoginView() override;
 
   // Initializes the webui login view.
@@ -105,6 +111,8 @@ class WebUILoginView : public views::View,
   }
 
  protected:
+  static void InitializeWebView(views::WebView* web_view);

[xiyuan, 2016/12/09 22:37:30]

nit: no need to expose this in header, put it in the anonymous namespace in cc
file

[jdufault, 2016/12/12 18:23:09]

This is needed for preloading the webview (done in a child CL).

+
   // Overridden from views::View:
   void Layout() override;
   void OnLocaleChanged() override;
@@ -148,6 +156,15 @@ class WebUILoginView : public views::View,
 
   content::NotificationRegistrar registrar_;
 
+  // WebView configuration options.
+  WebViewSettings settings_;

[xiyuan, 2016/12/09 22:37:30]

nit: const WebViewSettings if we don't need to change |settings_|.

[jdufault, 2016/12/12 18:23:09]

Done.

+
+  // True if the current webview instance (ie, GetWebUI()) has been reused.
+  bool is_reusing_webview_ = false;
+
+  // Prevents the webview from being destroyed while it is in use.
+  std::unique_ptr<SharedWebViewUsageHandle> webview_usage_handle_;
+
   // Converts keyboard events on the WebContents to accelerators.
   views::UnhandledKeyboardEventHandler unhandled_keyboard_event_handler_;