Make sure WebContents passed to chrome_page_zoom::Zoom() have a ZoomController.

chrome/browser/ui/zoom/zoom_controller.h

Index: chrome/browser/ui/zoom/zoom_controller.h
diff --git a/chrome/browser/ui/zoom/zoom_controller.h b/chrome/browser/ui/zoom/zoom_controller.h
index 4b5602ea7e47b7e9f760188d36200e40a1826bd4..1f67f545cf1e0f4928533dbc7e0c06782493d964 100644
--- a/chrome/browser/ui/zoom/zoom_controller.h
+++ b/chrome/browser/ui/zoom/zoom_controller.h
@@ -83,6 +83,13 @@ class ZoomController : public content::WebContentsObserver,
   void AddObserver(ZoomObserver* observer);
   void RemoveObserver(ZoomObserver* observer);
 
+  // Used to set whether the zoom notification bubble can be shown when the
+  // zoom level is changed for this controller. Default behavior is to show
+  // the bubble.
+  void SetShowsNotificationBubble(bool can_show_bubble) {
+    can_show_bubble_ = can_show_bubble;
+  }
+
   // Gets the current zoom level by querying HostZoomMap (if not in manual zoom
   // mode) or from the ZoomController local value otherwise.
   double GetZoomLevel() const;
@@ -121,6 +128,9 @@ class ZoomController : public content::WebContentsObserver,
   // change only affects sites with the given host.
   void UpdateState(const std::string& host);
 
+  // True if changes to zoom level can trigger the zoom notification bubble.
+  bool can_show_bubble_;
+
   // The current zoom mode.
   ZoomMode zoom_mode_;