Switch ZoomTabHelper to use WebContentsUserData.

chrome/browser/ui/tab_contents/tab_contents.h

Index: chrome/browser/ui/tab_contents/tab_contents.h
diff --git a/chrome/browser/ui/tab_contents/tab_contents.h b/chrome/browser/ui/tab_contents/tab_contents.h
index 2a1388f86dfd48fe8c576947a2bd2ddfb73517b6..0d4fbb2cfe7a77f4d920c1968366aeadb33b91eb 100644
--- a/chrome/browser/ui/tab_contents/tab_contents.h
+++ b/chrome/browser/ui/tab_contents/tab_contents.h
@@ -60,7 +60,6 @@ class WebIntentPickerCocoa;
 class WebIntentPickerController;
 class WebIntentPickerGtk;
 class WebUITestContentsCreator;
-class ZoomController;
 
 namespace browser_sync {
 class SyncedTabDelegate;
@@ -216,10 +215,6 @@ class TabContents : public content::WebContentsObserver {
     return web_intent_picker_controller_.get();
   }
 
-  ZoomController* zoom_controller() {
-    return zoom_controller_.get();
-  }
-
   // Overrides -----------------------------------------------------------------
 
   // content::WebContentsObserver overrides:
@@ -272,8 +267,6 @@ class TabContents : public content::WebContentsObserver {
   // Handles displaying a web intents picker to the user.
   scoped_ptr<WebIntentPickerController> web_intent_picker_controller_;
 
-  scoped_ptr<ZoomController> zoom_controller_;
-
   // Per-tab observers ---------------------------------------------------------
   // (These provide no API for callers; objects that need to exist 1:1 with tabs
   // and silently do their thing live here.)