Figure out the MIME type of shared WebUI resources more efficiently

content/browser/webui/shared_resources_data_source.h

Index: content/browser/webui/shared_resources_data_source.h
diff --git a/content/browser/webui/shared_resources_data_source.h b/content/browser/webui/shared_resources_data_source.h
index 53bf513bf74147c931bfdb9daf00cad662e13d3a..002bbd244cb2b06c507aaaef9242b3ffb52ac784 100644
--- a/content/browser/webui/shared_resources_data_source.h
+++ b/content/browser/webui/shared_resources_data_source.h
@@ -23,7 +23,9 @@ class SharedResourcesDataSource : public URLDataSource {
       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;