Replace run_selenium.py with Dart script that uses the browser controller for performance tests.

samples/third_party/dromaeo/htmlrunner.js

 // An version of Dromaeo's original htmlrunner adapted for the
 // Dart-based test driver.
 
 var _operations = [];
 var _N_RUNS = 5;
 var _nRanTests = 0;
 var _nTests = 0;
 var _T_DISTRIBUTION = 2.776;
 
 function startTest() {
@@ skipping 21 matching lines @@
     }
   }
   window.setTimeout(handler, 0);
 }
 
 function _postMessage(command, data) {
   var payload = { 'command': command };
   if (data) {
     payload['data'] = data;
   }
-  window.top.postMessage(JSON.stringify(payload), '*');
+  window.parent.postMessage(JSON.stringify(payload), '*');
 }
 
 function test(name, fn) {
   _nTests++;
   _operations.push(function () {
       // List of number of runs in seconds.
       var runsPerSecond = [];
       // Run the test several times.
       try {
         // TODO(antonm): use .setTimeout to schedule next run as JS
@@ skipping 80 matching lines @@
           });
 }
 
 function endTest() {
   _postMessage('inited', { 'nTests': _nTests });
 }
 
 function prep(fn) {
   _operations.push(fn);
 }