Generalize content::URLDataSource so that it can be used by the network service.

chrome/browser/search/thumbnail_source.h

Index: chrome/browser/search/thumbnail_source.h
diff --git a/chrome/browser/search/thumbnail_source.h b/chrome/browser/search/thumbnail_source.h
index 79d30955022c0236e21b8a03e77e622bf1e3d154..5f3f551136286aa060f53ca4f08357de32915257 100644
--- a/chrome/browser/search/thumbnail_source.h
+++ b/chrome/browser/search/thumbnail_source.h
@@ -41,7 +41,9 @@ class ThumbnailSource : public content::URLDataSource {
   scoped_refptr<base::SingleThreadTaskRunner> TaskRunnerForRequestPath(
       const std::string& path) const override;
   bool AllowCaching() const override;
-  bool ShouldServiceRequest(const net::URLRequest* request) const override;
+  bool ShouldServiceRequest(const GURL& url,
+                            content::ResourceContext* resource_context,
+                            int render_process_id) const override;
 
   // Extracts the |page_url| (e.g. cnn.com) and the |fallback_thumbnail_url|
   // fetchable from the server, if present, from the |path|. Visible for