Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/unittest/src/group_context.dart

+part of unittest;
+
+/// Setup and teardown functions for a group and its parents, the latter
+/// for chaining.
+class _GroupContext {
+  final _GroupContext parent;
+
+  /// Description text of the current test group.
+  final String _name;
+
+  /// Setup function called before each test in a group.
+  Function _testSetup;
+
+  get testSetup => _testSetup;
+
+  get parentSetup => (parent == null) ? null : parent.testSetup;
+
+  set testSetup(Function setup) {
+    var preSetup = parentSetup;
+    if (preSetup == null) {
+      _testSetup = setup;
+    } else {
+      _testSetup = () {
+        var f = preSetup();
+        if (f is Future) {
+          return f.then((_) => setup());
+        } else {
+          return setup();
+        }
+      };
+    }
+  }
+
+  /// Teardown function called after each test in a group.
+  Function _testTeardown;
+
+  get testTeardown => _testTeardown;
+
+  get parentTeardown => (parent == null) ? null : parent.testTeardown;
+
+  set testTeardown(Function teardown) {
+    var postTeardown = parentTeardown;
+    if (postTeardown == null) {
+      _testTeardown = teardown;
+    } else {
+      _testTeardown = () {
+        var f = teardown();
+        if (f is Future) {
+          return f.then((_) => postTeardown());
+        } else {
+          return postTeardown();
+        }
+      };
+    }
+  }
+
+  String get fullName => (parent == null || parent == _environment.rootContext)
+      ? _name
+      : "${parent.fullName}$groupSep$_name";
+
+  _GroupContext([this.parent, this._name = '']) {
+    _testSetup = parentSetup;
+    _testTeardown = parentTeardown;
+  }
+}