Fix type checks and display for JS interop types.

pkg/dev_compiler/karma.conf.js

 // Karma configuration
 // Generated on Mon Apr 20 2015 06:33:20 GMT-0700 (PDT)
 
 module.exports = function(config) {
   var configuration = {
 
     // base path that will be used to resolve all patterns (eg. files, exclude)
     basePath: '',
 
     // frameworks to use
     // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
     frameworks: ['mocha', 'requirejs', 'chai'],
 
     // list of files / patterns to load in the browser
     files: [
       {pattern: 'lib/js/amd/dart_sdk.js', included: false},
       {pattern: 'gen/codegen_output/pkg/*.js', included: false},
       {pattern: 'gen/codegen_output/language/**/*.js', included: false},
       {pattern: 'gen/codegen_output/corelib/**/*.js', included: false},
       {pattern: 'gen/codegen_output/lib/**/*.js', included: false},
+      {pattern: 'gen/codegen_tests/lib/**/*.txt', included: false},
       {pattern: 'test/browser/*.js', included: false},
       {pattern: 'node_modules/is_js/*.js', included: false},      
       'test-main.js',
     ],
 
     // list of files to exclude
     exclude: [],
 
     // preprocess matching files before serving them to the browser
     // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
     preprocessors: {
     },
 
     client: {
       captureConsole: false,
       mocha: {
         ui: 'tdd',
         timeout : 6000
       },
     },
 
     // test results reporter to use
     // possible values: 'dots', 'progress'
     // available reporters: https://npmjs.org/browse/keyword/karma-reporter
     reporters: ['progress'],
 
     // web server port
     port: 9876,
 
+    // Proxy requried to match expectations on where resources required by

[vsm, 2017/04/03 15:14:56]

requried -> required

[Jacob, 2017/04/03 15:33:05]

Done.

+    // tests are served from.
+    proxies: {
+      '/root_dart/tests/lib/': '/base/gen/codegen_tests/lib/'

[Jacob, 2017/04/01 00:51:13]

this matches the directory structure used by the regular dart-sdk tests.

+    },
+
     // enable / disable colors in the output (reporters and logs)
     colors: true,
 
     // level of logging
     // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
     logLevel: config.LOG_INFO,
 
     // enable / disable watching file and executing tests whenever any file changes
     autoWatch: true,
 
@@ skipping 29 matching lines @@
     // configuration.logLevel = config.LOG_DEBUG;
     configuration.client.captureConsole = true;
   }
 
   if (process.env.DDC_BROWSERS) {
     configuration.browsers = process.env.DDC_BROWSERS.split(':');
   }
 
   config.set(configuration);
 };