Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/string_scanner/test/utils.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.test.utils;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+/// Returns a matcher that asserts that a closure throws a [FormatException]
+/// with the given [message].
+Matcher throwsStringScannerException(String text) {
+  return throwsA(predicate((error) {
+    expect(error, new isInstanceOf<StringScannerException>());
+    expect(error.span.text, equals(text));
+    return true;
+  }));
+}