Fix type checks and display for JS interop types.

pkg/dev_compiler/karma.conf.js

Index: pkg/dev_compiler/karma.conf.js
diff --git a/pkg/dev_compiler/karma.conf.js b/pkg/dev_compiler/karma.conf.js
index e9041061fb0f3b83f1911b0800f6a7e1ee6f641c..54d0400ef9d789ff14f7fd3b8d79dd0626826c08 100644
--- a/pkg/dev_compiler/karma.conf.js
+++ b/pkg/dev_compiler/karma.conf.js
@@ -18,6 +18,7 @@ module.exports = function(config) {
       {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',
@@ -47,6 +48,12 @@ module.exports = function(config) {
     // 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,