Implement chromium component.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2011, 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("test_runner");
 
 #import("status_file_parser.dart");
 #import("test_progress.dart");
 #import("test_suite.dart");
 
@@ skipping 195 matching lines @@
         line = source.readLine();
       }
     };
   }
 
   void start() {
     Expect.isFalse(testCase.expectedOutcomes.contains(SKIP));
     stdout = new List<String>();
     stderr = new List<String>();
     if (testCase is BrowserTestCase) {
-      runCommand(testCase.compilerPath,
-                 testCase.compilerArguments,
+      BrowserTestCase browserTestCase = testCase;
+      runCommand(browserTestCase.compilerPath,
+                 browserTestCase.compilerArguments,
                  compilerExitHandler);
     } else {
       runCommand(testCase.executablePath, testCase.arguments, exitHandler);
     }
   }
 
   void runCommand(String executable,
                   List<String> arguments,
                   void exitHandler(int exitCode)) {
     process = new Process(executable, arguments);
@@ skipping 242 matching lines @@
       if (test.configuration['component'] == 'dartc') {
         _ensureDartcBatchRunnersStarted(test.executablePath);
         _getDartcBatchRunnerProcess().startTest(test);
       } else {
         new RunningProcess(test).start();
       }
       _numProcesses++;
     }
   }
 }