Refactor browser window zoom handling and enable zoom icon on all platforms.

chrome/browser/ui/cocoa/browser_window_controller.h

Index: chrome/browser/ui/cocoa/browser_window_controller.h
diff --git a/chrome/browser/ui/cocoa/browser_window_controller.h b/chrome/browser/ui/cocoa/browser_window_controller.h
index a1e787c8bad6d770aa42cf4644ec5153a1ddcf76..2d72077fec99f0a44eb97a545e6c10bbecab50d7 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller.h
+++ b/chrome/browser/ui/cocoa/browser_window_controller.h
@@ -223,6 +223,11 @@ class WebContents;
 // Sets whether or not the current page in the frontmost tab is bookmarked.
 - (void)setStarredState:(BOOL)isStarred;
 
+// Happens when the zoom level is changed in the active tab, the active tab is
+// changed, or a new browser window or tab is created. |canShowBubble| denotes
+// whether it would be appropriate to show a zoom bubble or not.
+- (void)zoomChangedForActiveTab:(BOOL)canShowBubble;
+
 // Return the rect, in WebKit coordinates (flipped), of the window's grow box
 // in the coordinate system of the content area of the currently selected tab.
 - (NSRect)selectedTabGrowBoxRect;