Add URL generator / json parser for getting start_page_token of changes.

google_apis/drive/drive_api_url_generator.h

Index: google_apis/drive/drive_api_url_generator.h
diff --git a/google_apis/drive/drive_api_url_generator.h b/google_apis/drive/drive_api_url_generator.h
index 089912744a28fea4d0e3831d2e213d6e995bb00d..720b29b32460d984d3266cff5e339d7c047b12d7 100644
--- a/google_apis/drive/drive_api_url_generator.h
+++ b/google_apis/drive/drive_api_url_generator.h
@@ -80,6 +80,9 @@ class DriveApiUrlGenerator {
   GURL GetTeamDriveListUrl(int max_results,
                            const std::string& page_token) const;
 
+  // Returns a URL to get the starting pageToken for listing future changes.
+  GURL GetChangesGetStartPageTokenUrl(const std::string& team_drive_id) const;
+
   // Returns a URL to fetch a list of changes.
   GURL GetChangesListUrl(bool include_deleted,
                          int max_results,