Fix #242, onion skin rendered not cleared if 0 frames

test/js/testutils/TestUtils.js

@@ -0,0 +1,22 @@
+(function () {
+  var ns = $.namespace('test.testutils');
+
+  ns.toFrameGrid = function (normalGrid) {
+    var frameGrid = [];
+    var w = normalGrid[0].length;
+    var h = normalGrid.length;
+    for (var x = 0 ; x < w ; x++) {
+      frameGrid[x] = [];
+      for (var y = 0 ; y < h ; y++) {
+        frameGrid[x][y] = normalGrid[y][x];
+      }
+    }
+    return frameGrid;
+  };
+
+  ns.frameEqualsGrid = function (frame, grid) {
+    frame.forEachPixel(function (color, col, row) {
+      expect(color).toBe(grid[row][col]);
+    });
+  };
+})();