Fix flickering window by deparenting before shutting bubble.

This cl revises https://codereview.chromium.org/886883002 in order to
fix the window-flickering issue by de-parenting the bubble window
prior to closing it.

BUG=444995

Review URL: https://codereview.chromium.org/887003006

(cherry picked from commit c9c22ca31db0aad109e7da30f84bbdc5284fe684)

Cr-Original-Commit-Position: refs/heads/master@{#315524}
Cr-Commit-Position: refs/branch-heads/2272@{#292}
Cr-Branched-From: 827a380cfdb31aa54c8d56e63ce2c3fd8c3ba4d4-refs/heads/master@{#310958}

diff --git a/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.h b/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.h
index cfcd3452..7293b4b 100644
--- a/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.h
+++ b/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.h

@@ -48,6 +48,8 @@
   ui::ScopedCrTrackingArea trackingArea_;
 }
 
+@property(nonatomic) ZoomBubbleControllerDelegate* delegate;
+
 // Creates the bubble for a parent window but does not show it.
 - (id)initWithParentWindow:(NSWindow*)parentWindow
                   delegate:(ZoomBubbleControllerDelegate*)delegate;

diff --git a/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.mm b/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.mm
index 60fbf5c2..74480a42 100644
--- a/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.mm
+++ b/chrome/browser/ui/cocoa/browser/zoom_bubble_controller.mm

@@ -75,6 +75,8 @@
 
 @implementation ZoomBubbleController
 
+@synthesize delegate = delegate_;
+
 - (id)initWithParentWindow:(NSWindow*)parentWindow
                   delegate:(ZoomBubbleControllerDelegate*)delegate {
   base::scoped_nsobject<InfoBubbleWindow> window(
@@ -126,6 +128,10 @@
 }
 
 - (void)onZoomChanged {
+  // |delegate_| may be set null by this object's owner.
+  if (!delegate_)
+    return;
+
   // TODO(shess): It may be appropriate to close the window if
   // |contents| or |zoomController| are NULL.  But they can be NULL in
   // tests.
@@ -169,8 +175,11 @@
 }
 
 - (void)windowWillClose:(NSNotification*)notification {
-  delegate_->OnClose();
-  delegate_ = NULL;
+  // |delegate_| may be set null by this object's owner.
+  if (delegate_) {
+    delegate_->OnClose();
+    delegate_ = NULL;
+  }
   [NSObject cancelPreviousPerformRequestsWithTarget:self
                                            selector:@selector(autoCloseBubble)
                                              object:nil];

diff --git a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.h b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.h
index 90ef008..db09902 100644
--- a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.h
+++ b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.h

@@ -33,6 +33,7 @@
 
   // Shows the zoom bubble for this decoration. If |auto_close| is YES, then
   // the bubble will automatically close after a fixed period of time.
+  // If a bubble is already showing, the |auto_close| timer is reset.
   void ShowBubble(BOOL auto_close);
 
   // Closes the zoom bubble.

diff --git a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
index 7306dd1..c015e70 100644
--- a/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm
+++ b/chrome/browser/ui/cocoa/location_bar/zoom_decoration.mm

@@ -23,6 +23,7 @@
 
 ZoomDecoration::~ZoomDecoration() {
   [bubble_ closeWithoutAnimation];
+  bubble_.delegate = nil;
 }
 
 bool ZoomDecoration::UpdateIfNecessary(
@@ -48,8 +49,12 @@
 }
 
 void ZoomDecoration::ShowBubble(BOOL auto_close) {
-  if (bubble_)
-    return;
+  if (bubble_) {
+    bubble_.delegate = nil;
+    [[bubble_.window parentWindow] removeChildWindow:bubble_.window];
+    [bubble_.window orderOut:nil];
+    [bubble_ closeWithoutAnimation];
+  }
 
   content::WebContents* web_contents = owner_->GetWebContents();
   if (!web_contents)
@@ -138,6 +143,7 @@
 }
 
 void ZoomDecoration::OnClose() {
+  bubble_.delegate = nil;
   bubble_ = nil;
 
   // If the page is at default zoom then hiding the zoom decoration