rebaseline_server: add urlSchemaVersion parameter

gm/rebaseline_server/static/loader.js

 /*
  * Loader:
  * Reads GM result reports written out by results.py, and imports
  * them into $scope.extraColumnHeaders and $scope.imagePairs .
  */
 var Loader = angular.module(
     'Loader',
     ['ConstantsModule']
 );
 
@@ skipping 408 matching lines @@
     };
     $scope.queryParameters.map[constants.KEY__EXTRACOLUMNS__BUILDER] =
         $scope.queryParameters.copiers.categoryValueMatch;
     $scope.queryParameters.map[constants.KEY__EXTRACOLUMNS__TEST] =
         $scope.queryParameters.copiers.categoryValueMatch;
 
     // Loads all parameters into $scope from the URL query string;
     // any which are not found within the URL will keep their current value.
     $scope.queryParameters.load = function() {
       var nameValuePairs = $location.search();
+
+      var urlSchemaVersion = nameValuePairs[constants.URL_KEY__SCHEMA_VERSION];
+      if (!urlSchemaVersion) {
+        $scope.urlSchemaVersionLoaded = 0;
+      } else if (urlSchemaVersion == constants.URL_VALUE__SCHEMA_VERSION__ALWAYS_CURRENT) {
+        $scope.urlSchemaVersionLoaded = constants.URL_VALUE__SCHEMA_VERSION__CURRENT;
+      } else {
+        $scope.urlSchemaVersionLoaded = urlSchemaVersion;
+      }
+
       angular.forEach($scope.queryParameters.map,
                       function(copier, paramName) {
                         copier.load(nameValuePairs, paramName);
                       }
                      );
     };
 
     // Saves all parameters from $scope into the URL query string.
     $scope.queryParameters.save = function() {
       var nameValuePairs = {};
+      nameValuePairs[constants.URL_KEY__SCHEMA_VERSION] = constants.URL_VALUE__SCHEMA_VERSION__CURRENT;
       angular.forEach($scope.queryParameters.map,
                       function(copier, paramName) {
                         copier.save(nameValuePairs, paramName);
                       }
                      );
       $location.search(nameValuePairs);
     };
 
 
     //
@@ skipping 474 matching lines @@
      */
     $scope.getImageDiffRelativeUrl = function(imagePair) {
       var before =
           imagePair[constants.KEY__IMAGEPAIRS__IMAGE_A_URL] + "-vs-" +
           imagePair[constants.KEY__IMAGEPAIRS__IMAGE_B_URL];
       return before.replace(/[^\w\-]/g, "_") + ".png";
     }
 
   }
 );