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 45 matching lines @@
   bool anchor_to_view = !is_fullscreen ||
       browser_view->immersive_mode_controller()->IsRevealed();
   views::View* anchor_view = anchor_to_view ?
       browser_view->GetLocationBarView()->zoom_view() : NULL;
 
   // Find the extension that initiated the zoom change, if any.
   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() {
+  // Prevent inadvertent re-use of this bubble.

[sky, 2014/11/12 21:48:55]

This isn't entirely clear. Maybe something like Close() is async, but we don't
to use zoom_bubble_ after this. Additionally web_contents_ may have been
destroyed.

[wjmaclean, 2014/11/12 22:00:00]

Done.

I assume you meant "Widget's Close() is async ..."

+  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 156 matching lines @@
 }
 
 void ZoomBubbleView::OnImmersiveRevealStarted() {
   CloseBubble();
 }
 
 void ZoomBubbleView::OnImmersiveModeControllerDestroyed() {
   immersive_mode_controller_ = NULL;
 }
 
-void ZoomBubbleView::WindowClosing() {

[sky, 2014/11/12 21:48:55]

You should still keep this. The reason you want this too is that you can end up
here if the OS triggers the close.

[wjmaclean, 2014/11/12 22:00:01]

Sounds fair ... didn't realize that would happen.

Restored.

-  // |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() {}