rebaseline_server: image URLs are relative to JSON file's location

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 146 matching lines @@
                                        [constants.KEY__VALUES_AND_COUNTS]);
 
           // Associative array of partial string matches per category.
           $scope.categoryValueMatch = {};
           $scope.categoryValueMatch.builder = "";
           $scope.categoryValueMatch.test = "";
 
           // If any defaults were overridden in the URL, get them now.
           $scope.queryParameters.load();
 
+          // Any image URLs which are relative should be relative to the JSON
+          // file's source directory; absolute URLs should be left alone.
+          var baseUrlKey = constants.KEY__IMAGESETS__FIELD__BASE_URL;
+          angular.forEach(
+            $scope.imageSets,
+            function(imageSet) {
+              var baseUrl = imageSet[baseUrlKey];
+              if ((baseUrl.substring(0, 1) != '/') &&
+                  (baseUrl.indexOf('://') == -1)) {
+                imageSet[baseUrlKey] = $scope.resultsToLoad + '/../' + baseUrl;
+              }
+            }
+          );
+
           $scope.updateResults();
           $scope.loadingMessage = "";
           $scope.windowTitle = "Current GM Results";
         }
       }
     ).error(
       function(data, status, header, config) {
         $scope.loadingMessage = "FAILED to load.";
         $scope.windowTitle = "Failed to Load GM Results";
       }
@@ skipping 612 matching lines @@
      */
     $scope.getImageDiffRelativeUrl = function(imagePair) {
       var before =
           imagePair[constants.KEY__IMAGE_A_URL] + "-vs-" +
           imagePair[constants.KEY__IMAGE_B_URL];
       return before.replace(/[^\w\-]/g, "_") + ".png";
     }
 
   }
 );