Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/filter/json.dart

Index: third_party/pkg/angular/lib/filter/json.dart
diff --git a/third_party/pkg/angular/lib/filter/json.dart b/third_party/pkg/angular/lib/filter/json.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f2c0efa80dfcf2c1c93dbf09fd12b6d27c6366f2
--- /dev/null
+++ b/third_party/pkg/angular/lib/filter/json.dart
@@ -0,0 +1,14 @@
+part of angular.filter;
+
+/**
+ * Allows you to convert a JavaScript object into JSON string. This filter is
+ * mostly useful for debugging.
+ *
+ * Usage:
+ *
+ *     {{ json_expression | json }}
+ */
+@NgFilter(name:'json')
+class JsonFilter {
+  call(text) => JSON.encode(text);
+}