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

chrome/browser/chromeos/tab_first_render_watcher.cc

Index: chrome/browser/chromeos/tab_first_render_watcher.cc
diff --git a/chrome/browser/chromeos/tab_first_render_watcher.cc b/chrome/browser/chromeos/tab_first_render_watcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fecb253e5568b7f6e686a83b6c12f886edd3e99c
--- /dev/null
+++ b/chrome/browser/chromeos/tab_first_render_watcher.cc
@@ -0,0 +1,54 @@
+// 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.
+
+#include "chrome/browser/chromeos/tab_first_render_watcher.h"
+
+#include "content/browser/renderer_host/render_widget_host.h"
+#include "content/common/content_notification_types.h"
+#include "content/common/notification_details.h"
+#include "content/common/notification_source.h"
+
+namespace chromeos {
+
+TabFirstRenderWatcher::TabFirstRenderWatcher(TabContents* tab,
+                                             Delegate* delegate)
+    : state_(NONE),
+      tab_contents_(tab),
+      delegate_(delegate) {
+  registrar_.Add(this,
+      content::NOTIFICATION_RENDER_VIEW_HOST_CREATED_FOR_TAB,
+      Source<TabContents>(tab_contents_));
+  registrar_.Add(this,
+      content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
+      Source<TabContents>(tab_contents_));
+}
+
+void TabFirstRenderWatcher::Observe(int type,
+    const NotificationSource& source, const NotificationDetails& details) {
+  switch (type) {
+    case content::NOTIFICATION_RENDER_VIEW_HOST_CREATED_FOR_TAB: {
+      RenderWidgetHost* rwh = Details<RenderWidgetHost>(details).ptr();
+      registrar_.Add(this,
+          content::NOTIFICATION_RENDER_WIDGET_HOST_DID_PAINT,
+          Source<RenderWidgetHost>(rwh));
+      break;
+    }
+    case content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME:
+      if (state_ == NONE) {
+        state_ = LOADED;
+        delegate_->OnTabMainFrameLoaded();
+      }
+      break;
+    case content::NOTIFICATION_RENDER_WIDGET_HOST_DID_PAINT:
+      if (state_ == LOADED) {
+        state_ = FIRST_PAINT;
+        delegate_->OnTabMainFrameFirstRender();
+      }
+      break;
+    default:
+      NOTREACHED() << "unknown type" << type;
+  }
+}
+
+}  // namespace chromeos