Don't re-use a zoom bubble unless it has the same web-contents.

chrome/browser/ui/views/location_bar/zoom_bubble_view.cc

 // Copyright (c) 2012 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/ui/views/location_bar/zoom_bubble_view.h"
 
 #include "base/i18n/rtl.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chrome_page_zoom.h"
@@ skipping 51 matching lines @@
   ZoomController* zoom_controller =
       ZoomController::FromWebContents(web_contents);
   const extensions::Extension* extension = zoom_controller->last_extension();
 
   // If the bubble is already showing in this window and the zoom change was not
   // initiated by an extension, then the bubble can be reused and only the label
   // text needs to be updated.
   if (zoom_bubble_ &&
       zoom_bubble_->GetAnchorView() == anchor_view &&
       !extension) {
+    DCHECK_EQ(web_contents, zoom_bubble_->web_contents_);
     zoom_bubble_->Refresh();
     return;
   }
 
   // If the bubble is already showing but in a different tab, the current
   // bubble must be closed and a new one created.
   CloseBubble();
 
   zoom_bubble_ = new ZoomBubbleView(anchor_view,
                                     web_contents,
@@ skipping 85 matching lines @@
 void ZoomBubbleView::Refresh() {
   ZoomController* zoom_controller =
       ZoomController::FromWebContents(web_contents_);
   int zoom_percent = zoom_controller->GetZoomPercent();
   label_->SetText(
       l10n_util::GetStringFUTF16Int(IDS_TOOLTIP_ZOOM, zoom_percent));
   StartTimerIfNecessary();
 }
 
 void ZoomBubbleView::Close() {
+  // Widget's Close() is async, but we don't want to use zoom_bubble_ after
+  // this. Additionally web_contents_ may have been destroyed.
+  zoom_bubble_ = NULL;
+  web_contents_ = NULL;
   GetWidget()->Close();
 }
 
 void ZoomBubbleView::SetExtensionInfo(const extensions::Extension* extension) {
   DCHECK(extension);
   extension_info_.id = extension->id();
   extension_info_.name = extension->name();
 
   ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
   const gfx::ImageSkia& default_extension_icon_image =
@@ skipping 166 matching lines @@
 void ZoomBubbleView::WindowClosing() {
   // |zoom_bubble_| can be a new bubble by this point (as Close(); doesn't
   // call this right away). Only set to NULL when it's this bubble.
   if (zoom_bubble_ == this)
     zoom_bubble_ = NULL;
 }
 
 ZoomBubbleView::ZoomBubbleExtensionInfo::ZoomBubbleExtensionInfo() {}
 
 ZoomBubbleView::ZoomBubbleExtensionInfo::~ZoomBubbleExtensionInfo() {}