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

mojo/public/dart/third_party/test/pubspec.yaml

+name: test
+version: 0.12.4+7
+author: Dart Team <misc@dartlang.org>
+description: A library for writing dart unit tests.
+homepage: https://github.com/dart-lang/test
+environment:
+  sdk: '>=1.11.0 <1.14.0'
+dependencies:
+  analyzer: '>=0.23.0 <0.27.0'
+  args: '>=0.12.1 <0.14.0'
+  async: '>=1.3.0 <2.0.0'
+  barback: '>=0.14.0 <0.16.0'
+  collection: '^1.1.0'
+  crypto: '^0.9.0'
+  glob: '^1.0.0'
+  http_multi_server: '^1.0.0'
+  http_parser: '>=0.0.2 <2.0.0'
+  path: '^1.2.0'
+  pool: '^1.1.0'
+  pub_semver: '^1.0.0'
+  shelf: '>=0.6.0 <0.7.0'
+  shelf_static: '^0.2.0'
+  shelf_web_socket: '^0.0.1'
+  source_map_stack_trace: '^1.0.0'
+  source_maps: '^0.10.1'
+  source_span: '^1.0.0'
+  stack_trace: '^1.2.1'
+  string_scanner: '^0.1.1'
+  yaml: '>=0.9.0 <3.0.0'
+
+  # Use a tight version constraint to ensure that a constraint on matcher
+  # properly constrains all features it provides.
+  matcher: '>=0.12.0 <0.12.1'
+dev_dependencies:
+  fake_async: '^0.1.2'
+  scheduled_test: '^0.12.2'