[ChromeOS] Freezes WebUI OOBE/Login window until tab is rendered.

chrome/browser/chromeos/tab_first_render_watcher.h

Index: chrome/browser/chromeos/tab_first_render_watcher.h
diff --git a/chrome/browser/chromeos/tab_first_render_watcher.h b/chrome/browser/chromeos/tab_first_render_watcher.h
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+++ b/chrome/browser/chromeos/tab_first_render_watcher.h
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+// Copyright (c) 2011 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_TAB_FIRST_RENDER_WATCHER_H_
+#define CHROME_BROWSER_CHROMEOS_TAB_FIRST_RENDER_WATCHER_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "content/common/notification_observer.h"
+#include "content/common/notification_registrar.h"
+
+class TabContents;
+
+namespace chromeos {
+
+// This class watches given TabContent's loading and rendering state change.
+// TODO(xiyuan): Move this to a proper place and share with HTMLDialogView.
+class TabFirstRenderWatcher : public NotificationObserver {
+ public:
+  class Delegate {
+   public:
+    virtual void OnTabMainFrameLoaded() = 0;
+    virtual void OnTabMainFrameFirstRender() = 0;
+  };
+
+  TabFirstRenderWatcher(TabContents* tab, Delegate* delegate);
+
+ private:
+  // Overridden from NotificationObserver
+  virtual void Observe(int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  enum State {
+    NONE,
+    LOADED,        // Renderer loaded the page.
+    FIRST_PAINT,   // 1st paint event after the page is loaded.
+  };
+  State state_;
+
+  // TabContents that this class watches.
+  TabContents* tab_contents_;
+
+  // Delegate to notify.
+  Delegate* delegate_;
+
+  NotificationRegistrar registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(TabFirstRenderWatcher);
+};
+
+}   // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_TAB_FIRST_RENDER_WATCHER_H_