Add support for running tests on Dartium.

lib/src/runner/browser/browser_manager.dart

Index: lib/src/runner/browser/browser_manager.dart
diff --git a/lib/src/runner/browser/browser_manager.dart b/lib/src/runner/browser/browser_manager.dart
index 03817e6026b16aa6dc0448403036392ef9d90823..6fd0a8abeb5b6fc4b3622abc1ad54e7a93bcd747 100644
--- a/lib/src/runner/browser/browser_manager.dart
+++ b/lib/src/runner/browser/browser_manager.dart
@@ -64,7 +64,7 @@ class BrowserManager {
         var metadata = new Metadata.deserialize(test['metadata']);
         var testChannel = suiteChannel.virtualChannel(test['channel']);
         return new IframeTest(test['name'], metadata, testChannel);
-      }), path: path, platform: "Chrome");
+      }), path: path);
     });
   }
 }