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

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

Index: chrome/browser/ui/views/location_bar/zoom_bubble_view.cc
diff --git a/chrome/browser/ui/views/location_bar/zoom_bubble_view.cc b/chrome/browser/ui/views/location_bar/zoom_bubble_view.cc
index 081b8b2e8256a50a55c2c71cda00e17a0e5a41c7..e1d4506e5bf37489337d84f3f8677da70ae1d8e3 100644
--- a/chrome/browser/ui/views/location_bar/zoom_bubble_view.cc
+++ b/chrome/browser/ui/views/location_bar/zoom_bubble_view.cc
@@ -63,12 +63,10 @@ void ZoomBubbleView::ShowBubble(content::WebContents* web_contents,
       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;
   }
@@ -174,6 +172,9 @@ void ZoomBubbleView::Refresh() {
 }
 
 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();
 }
 
@@ -350,13 +351,6 @@ 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() {}