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

content/browser/resource_context_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RESOURCE_CONTEXT_IMPL_H_
 #define CONTENT_BROWSER_RESOURCE_CONTEXT_IMPL_H_
 
 #include "content/public/browser/resource_context.h"
 
 class ChromeBlobStorageContext;
 class WebKitContext;
 
 namespace webkit_database {
 class DatabaseTracker;
 }
 
 namespace content {
 
 class BrowserContext;
+class HostZoomMap;
 
 // Getters for objects that are part of BrowserContext which are also used on
 // the IO thread. These are only accessed by content so they're not on the
 // public API.
 webkit_database::DatabaseTracker* GetDatabaseTrackerForResourceContext(
     ResourceContext* resource_context);
 WebKitContext* GetWebKitContextForResourceContext(
     ResourceContext* resource_context);
 ChromeBlobStorageContext* GetChromeBlobStorageContextForResourceContext(
     ResourceContext* resource_context);
+HostZoomMap* GetHostZoomMapForResourceContext(ResourceContext* context);
 
 // Initialize the above data on the ResourceContext from a given BrowserContext.
 void InitializeResourceContext(BrowserContext* browser_context);
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RESOURCE_CONTEXT_IMPL_H_