Allow extensions of the ManifestParser outside of the content/ layer.

content/public/renderer/content_renderer_client.cc

 // 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.
 
 #include "content/public/renderer/content_renderer_client.h"
 
 #include "media/base/renderer_factory.h"
 #include "third_party/WebKit/public/web/WebPluginPlaceholder.h"
 
 namespace content {
@@ skipping 197 matching lines @@
     RenderFrame* render_frame,
     const std::string& mime_type,
     const GURL& original_url) {
   return nullptr;
 }
 
 std::string ContentRendererClient::GetUserAgentOverrideForURL(const GURL& url) {
   return std::string();
 }
 
+bool ContentRendererClient::ParseManifestProperty(
+    const std::string& key, const base::Value& value) {
+  return false;
+}
+
 }  // namespace content