For OSX, make it so that notifications only start resizing after the first paint is done.

chrome/browser/notifications/balloon_host.cc

 // Copyright (c) 2010 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/notifications/balloon_host.h"
 
 #include "chrome/browser/browser_list.h"
 #include "chrome/browser/extensions/extension_process_manager.h"
 #include "chrome/browser/notifications/balloon.h"
 #include "chrome/browser/notifications/notification.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "chrome/browser/renderer_host/site_instance.h"
 #include "chrome/browser/renderer_preferences_util.h"
 #include "chrome/common/bindings_policy.h"
 #include "chrome/common/notification_service.h"
 #include "chrome/common/notification_type.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/renderer_preferences.h"
 #include "chrome/common/url_constants.h"
 #include "webkit/glue/webpreferences.h"
 
+namespace {
+class BalloonPaintObserver : public RenderWidgetHost::PaintObserver {
+ public:
+  explicit BalloonPaintObserver(BalloonHost* balloon_host)
+      : balloon_host_(balloon_host) {
+  }
+
+  virtual void RenderWidgetHostWillPaint(RenderWidgetHost* rhw) {}
+  virtual void RenderWidgetHostDidPaint(RenderWidgetHost* rwh);
+
+ private:
+  BalloonHost* balloon_host_;
+
+  DISALLOW_COPY_AND_ASSIGN(BalloonPaintObserver);
+};
+
+void BalloonPaintObserver::RenderWidgetHostDidPaint(RenderWidgetHost* rwh) {
+  balloon_host_->RenderWidgetHostDidPaint();
+  // WARNING: we may have been deleted (if the balloon host cleared the paint
+  // observer).
+}
+
+}  // namespace
+
 BalloonHost::BalloonHost(Balloon* balloon)
     : render_view_host_(NULL),
       balloon_(balloon),
       initialized_(false),
       should_notify_on_disconnect_(false),
       enable_dom_ui_(false) {
   DCHECK(balloon_);
 
   // If the notification is for an extension URL, make sure to use the extension
   // process to render it, so that it can communicate with other views in the
@@ skipping 52 matching lines @@
 
 void BalloonHost::Close(RenderViewHost* render_view_host) {
   balloon_->CloseByScript();
   NotifyDisconnect();
 }
 
 void BalloonHost::RenderViewCreated(RenderViewHost* render_view_host) {
   render_view_host->Send(new ViewMsg_DisableScrollbarsForSmallWindows(
       render_view_host->routing_id(), balloon_->min_scrollbar_size()));
   render_view_host->WasResized();
+#if !defined(OS_MACOSX)
   render_view_host->EnablePreferredSizeChangedMode(
       kPreferredSizeWidth | kPreferredSizeHeightThisIsSlow);
+#endif
 }
 
 void BalloonHost::RenderViewReady(RenderViewHost* render_view_host) {
   should_notify_on_disconnect_ = true;
   NotificationService::current()->Notify(
       NotificationType::NOTIFY_BALLOON_CONNECTED,
       Source<BalloonHost>(this), NotificationService::NoDetails());
 }
 
 void BalloonHost::RenderViewGone(RenderViewHost* render_view_host) {
@@ skipping 84 matching lines @@
     rvh->AllowBindings(BindingsPolicy::DOM_UI);
   }
 
   // Do platform-specific initialization.
   render_view_host_ = rvh;
   InitRenderWidgetHostView();
   DCHECK(render_widget_host_view());
 
   rvh->set_view(render_widget_host_view());
   rvh->CreateRenderView(string16());
+#if defined(OS_MACOSX)
+  rvh->set_paint_observer(new BalloonPaintObserver(this));
+#endif
   rvh->NavigateToURL(balloon_->notification().content_url());
 
   initialized_ = true;
 }
 
 void BalloonHost::EnableDOMUI() {
   DCHECK(render_view_host_ == NULL) <<
       "EnableDOMUI has to be called before a renderer is created.";
   enable_dom_ui_ = true;
 }
 
 void BalloonHost::UpdateInspectorSetting(const std::string& key,
                                          const std::string& value) {
   RenderViewHostDelegateHelper::UpdateInspectorSetting(
       GetProfile(), key, value);
 }
 
 void BalloonHost::ClearInspectorSettings() {
   RenderViewHostDelegateHelper::ClearInspectorSettings(GetProfile());
 }
 
-BalloonHost::~BalloonHost() {}
+void BalloonHost::RenderWidgetHostDidPaint() {
+  render_view_host_->set_paint_observer(NULL);
+  render_view_host_->EnablePreferredSizeChangedMode(
+      kPreferredSizeWidth | kPreferredSizeHeightThisIsSlow);
+}
+
+BalloonHost::~BalloonHost() {
+  DCHECK(!render_view_host_);
+}
 
 void BalloonHost::NotifyDisconnect() {
   if (!should_notify_on_disconnect_)
     return;
 
   should_notify_on_disconnect_ = false;
   NotificationService::current()->Notify(
       NotificationType::NOTIFY_BALLOON_DISCONNECTED,
       Source<BalloonHost>(this), NotificationService::NoDetails());
 }