Make getLineDash return [] instead of null if it has not yet been set.

tests/html/canvasrenderingcontext2d_test.dart

Index: tests/html/canvasrenderingcontext2d_test.dart
diff --git a/tests/html/canvasrenderingcontext2d_test.dart b/tests/html/canvasrenderingcontext2d_test.dart
index 9cafb0d8c9f5296b077b44dadae515133c010ea5..93e82e7129bc6fc14a72a9edbce438edda3aba7a 100644
--- a/tests/html/canvasrenderingcontext2d_test.dart
+++ b/tests/html/canvasrenderingcontext2d_test.dart
@@ -243,6 +243,17 @@ main() {
     });
   });
 
+  group('linedash', () {
+    setUp(setupFunc);
+    tearDown(tearDownFunc);
+
+    test('setLineDash', () {
+      expect(context.getLineDash(), equals([]));
+      List<num> old=context.getLineDash();

[blois, 2013/10/22 00:50:40]

old = context...

+      context.setLineDash(old);
+    });
+  });
+
   group('arc', () {
     setUp(setupFunc);
     tearDown(tearDownFunc);