Allow multiple dart <script> tags in .sky files

sky/tests/modules/resources/with-dart-import.sky

Index: sky/tests/modules/resources/with-dart-import.sky
diff --git a/sky/tests/modules/resources/with-dart-import.sky b/sky/tests/modules/resources/with-dart-import.sky
new file mode 100644
index 0000000000000000000000000000000000000000..a8fce617f105f46e194fa39dbbc60f9e6875c7e6
--- /dev/null
+++ b/sky/tests/modules/resources/with-dart-import.sky
@@ -0,0 +1,12 @@
+<script>
+import 'dart-import.dart' as base;
+// Use the dart import so it doesn't ignore it.
+class TestClass extends base.BaseClass {
+}
+
+bool didInit = false;
+
+void init() {
+    didInit = (new TestClass() != null);
+}
+</script>