chore(test): migrate Dart tests to package:test

Instead of running with karma and the karma-dart shim, run dart
tests directly using the new package:test runner. This migrates
away from package:unittest.

Fixes a couple tests, mostly associated with depending on absolute
URLs or editing the test providers after an injector had already
been created.

Remove karma-dart and associated files. Change gupfiles to run tests
via `pub run test` instead.

tools/build/pubtest.js

@@ -0,0 +1,51 @@
+var util = require('./util');
+var spawn = require('child_process').spawn;
+var glob = require('glob');
+var path = require('path');
+var fs = require('fs');
+var process = require('process');
+var createTestMain = require('./create_dart_test_main.js')
+
+function filterExclusiveTestFiles(files, dir) {
+  return files.filter(function(file) {
+    // TODO(juliemr): revisit if readFileSync becomes too slow.
+    // At the moment, this takes <100ms for all of angular2.
+    var text = fs.readFileSync(path.join(dir, file));
+    var iit = text.indexOf('iit(');
+    var ddescribe = text.indexOf('ddescribe(');
+    return (iit !== -1 || ddescribe !== -1);
+  });
+}
+
+module.exports = function(config) {
+  var platform = config.platform || 'dartium';
+  var pubArgs = ['run', 'test', '-p', platform];
+  var env = process.env;
+  var exclusive = false;
+  if (config.dartiumTmpdir) {
+    env['PATH'] = env['PATH'] + ':' + config.dartiumTmpdir;
+  }
+
+  testFiles = glob.sync(path.join(config.files), {cwd: config.dir});
+
+  if (config.useExclusiveTests) {
+    var filtered = filterExclusiveTestFiles(testFiles, config.dir);
+    if (filtered.length) {
+      exclusive = true;
+      pubArgs.push('--tags');
+      pubArgs.push('solo');
+      testFiles = filtered;
+    }
+  }
+
+  if (config.bunchFiles && !exclusive) {
+    var bigFile = createTestMain(config.dir, testFiles);
+    testFiles = [bigFile];
+  }
+
+  pubArgs = pubArgs.concat(testFiles);
+
+  return util.processToPromise(spawn(config.command, pubArgs, {
+    cwd: config.dir, stdio: 'inherit', env: env
+  }));
+};