Adding Angular and dependent packages for testing

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

Index: third_party/pkg/angular/lib/filter/lowercase.dart
diff --git a/third_party/pkg/angular/lib/filter/lowercase.dart b/third_party/pkg/angular/lib/filter/lowercase.dart
new file mode 100644
index 0000000000000000000000000000000000000000..650229c95a06eb8dadaca58056593f3d19d839ed
--- /dev/null
+++ b/third_party/pkg/angular/lib/filter/lowercase.dart
@@ -0,0 +1,13 @@
+part of angular.filter;
+
+/**
+ * Converts string to lowercase.
+ *
+ * Usage:
+ *
+ *     {{ lowercase_expression | lowercase }}
+ */
+@NgFilter(name:'lowercase')
+class LowercaseFilter {
+  call(String text) => text == null ? text : text.toLowerCase();
+}