Figure out the MIME type of shared WebUI resources more efficiently

content/browser/webui/shared_resources_data_source.h

 // Copyright (c) 2011 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_WEBUI_SHARED_RESOURCES_DATA_SOURCE_H_
 #define CONTENT_BROWSER_WEBUI_SHARED_RESOURCES_DATA_SOURCE_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/browser/url_data_source.h"
 
 namespace content {
 
 // A DataSource for chrome://resources/ URLs.
 class SharedResourcesDataSource : public URLDataSource {
  public:
   SharedResourcesDataSource();
 
   // URLDataSource implementation.
   std::string GetSource() const override;
   void StartDataRequest(
       const std::string& path,
       int render_process_id,
       int render_frame_id,
       const URLDataSource::GotDataCallback& callback) override;
-  std::string GetMimeType(const std::string&) const override;
+  std::string GetMimeType(const std::string& path) const override;
+  base::MessageLoop* MessageLoopForRequestPath(
+        const std::string& path) const override;
   std::string GetAccessControlAllowOriginForOrigin(
       const std::string& origin) const override;
 
  private:
   ~SharedResourcesDataSource() override;
 
   DISALLOW_COPY_AND_ASSIGN(SharedResourcesDataSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEBUI_SHARED_RESOURCES_DATA_SOURCE_H_