Support passing DartVM flags via DART_FLAGS.

tools/testing/dart/test_suite.dart

 // Copyright (c) 2012, 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_suite");
 
 #import("dart:io");
 #import("status_file_parser.dart");
 #import("test_runner.dart");
 #import("multitest.dart");
@@ skipping 459 matching lines @@
           break;
         case 'dartium':
           // No compilation phase.
           compilerExecutable = null;
           compilerArgs = null;
           break;
         default:
           Expect.fail('unimplemented component $component');
       }
 
-      String executable = dumpRenderTreeFilename;
       List<String> args;
       if (component == 'webdriver') {
-        executable = 'python';
-        if (new Platform().operatingSystem() == 'windows') {
-          // For Windows, the first command, must have the Windows 
-          // slash direction.
-          // TODO(efortuna): Get rid of this hack when issue 1306 is fixed.
-          executable = executable.replaceAll('/', '\\');
-        }
         args = ['$dartDir/tools/testing/run_selenium.py', '--out=$htmlPath', 
             '--browser=${configuration["browser"]}'];
       } else {
-        args = ['--no-timeout'];
+        args = [
+            '$dartDir/tools/testing/drt-trampoline.py',
+            dumpRenderTreeFilename,
+            '--no-timeout'
+        ];
         if (component == 'dartium') {
           var dartFlags = ['--ignore-unrecognized-flags'];
           if (configuration["checked"]) {
             dartFlags.add('--enable_asserts');
             dartFlags.add("--enable_type_checks");
           }
           dartFlags.addAll(vmOptions);
           args.add('--dart-flags=${Strings.join(dartFlags, " ")}');
         }
         args.add(htmlPath);
       }
       // Create BrowserTestCase and queue it.
       var testCase = new BrowserTestCase(
           testName,
           compilerExecutable,
           compilerArgs,
-          executable,
+          'python',
           args,
           configuration,
           completeHandler,
           expectations,
           optionsFromFile['isNegative']);
       doTest(testCase);
     }
   }
 
   bool get requiresCleanTemporaryDirectory() =>
@@ skipping 545 matching lines @@
  * $noCrash tests are expected to be flaky but not crash
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
 """;
     print(report);
    }
 }