Move creation and ownership of HostZoomMap to content instead of having every embedder do this.

content/public/browser/browser_context.h

Index: content/public/browser/browser_context.h
===================================================================
--- content/public/browser/browser_context.h	(revision 122827)
+++ content/public/browser/browser_context.h	(working copy)
@@ -38,7 +38,6 @@
 
 class DownloadManager;
 class GeolocationPermissionContext;
-class HostZoomMap;
 class ResourceContext;
 class SpeechInputPreferences;
 
@@ -96,9 +95,6 @@
   // Returns the resource context.
   virtual ResourceContext* GetResourceContext() = 0;
 
-  // Returns the Hostname <-> Zoom Level map for this context.
-  virtual HostZoomMap* GetHostZoomMap() = 0;
-
   // Returns the geolocation permission context for this context.
   virtual GeolocationPermissionContext* GetGeolocationPermissionContext() = 0;