Pass actual TestPlatform and OperatingSystem values to Suite.

lib/src/runner/browser/server.dart

Index: lib/src/runner/browser/server.dart
diff --git a/lib/src/runner/browser/server.dart b/lib/src/runner/browser/server.dart
index 1383bb3bc9e3423854a40b8b8d122639c22b8651..f2a3624cb7896f3ff5891be7db81107fee125ce9 100644
--- a/lib/src/runner/browser/server.dart
+++ b/lib/src/runner/browser/server.dart
@@ -297,15 +297,13 @@ void main() {
     var browserManager = await _browserManagerFor(browser);
     if (_closed) return null;
 
-    var suite;
     if (browserManager != null) {
-      suite = await browserManager.loadSuite(path, suiteUrl, metadata,
+      var suite = await browserManager.loadSuite(path, suiteUrl, metadata,
           mapper: browser.isJS ? _mappers[path] : null);
       if (_closed) return null;
+      if (suite != null) return suite;
     }
 
-    if (suite != null) return suite.change(platform: browser.name);
-
     // If the browser manager fails to load a suite and the server isn't
     // closed, it's probably because the browser failed. We emit the failure
     // here to ensure that it gets surfaced.