Move ZoomObserver, ZoomController and ZoomEventManager to components/.

chrome/browser/ui/zoom/chrome_zoom_level_prefs.h

Index: chrome/browser/ui/zoom/chrome_zoom_level_prefs.h
diff --git a/chrome/browser/ui/zoom/chrome_zoom_level_prefs.h b/chrome/browser/ui/zoom/chrome_zoom_level_prefs.h
index f01409c28f496dd021ffa58717940d28feed114f..580eb5e5cfe269fd249b8614ddec9d64c39fa5ab 100644
--- a/chrome/browser/ui/zoom/chrome_zoom_level_prefs.h
+++ b/chrome/browser/ui/zoom/chrome_zoom_level_prefs.h
@@ -18,14 +18,18 @@
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/zoom_level_delegate.h"
 
-class ZoomEventManager;
-
 namespace base {
 class DictionaryValue;
 }
 
+namespace extensions {
+class ZoomEventManager;
+}
+
 namespace chrome {
 
+using extensions::ZoomEventManager;
+
 // A class to manage per-partition default and per-host zoom levels in Chrome's
 // preference system. It implements an interface between the content/ zoom
 // levels in HostZoomMap and Chrome's preference system. All changes