Revert of Allow new zoom bubble to override current one.

chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm

Index: chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
diff --git a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
index ed9b67766e4a70aba640857db600411219cbf16b..7306dd10c75c8b4cea9d06142bcf406b21529732 100644
--- a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
+++ b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
@@ -23,7 +23,6 @@
 
 ZoomDecoration::~ZoomDecoration() {
   [bubble_ closeWithoutAnimation];
-  bubble_.delegate = nil;
 }
 
 bool ZoomDecoration::UpdateIfNecessary(
@@ -49,8 +48,8 @@
 }
 
 void ZoomDecoration::ShowBubble(BOOL auto_close) {
-  ZoomBubbleController* old_bubble = bubble_;
-  old_bubble.delegate = nil;
+  if (bubble_)
+    return;
 
   content::WebContents* web_contents = owner_->GetWebContents();
   if (!web_contents)
@@ -69,9 +68,6 @@
   bubble_ = [[ZoomBubbleController alloc] initWithParentWindow:[field window]
                                                       delegate:this];
   [bubble_ showAnchoredAt:anchor autoClose:auto_close];
-
-  [old_bubble.window orderOut:nil];
-  [old_bubble closeWithoutAnimation];
 }
 
 void ZoomDecoration::CloseBubble() {
@@ -142,7 +138,6 @@
 }
 
 void ZoomDecoration::OnClose() {
-  bubble_.delegate = nil;
   bubble_ = nil;
 
   // If the page is at default zoom then hiding the zoom decoration