Remove need to instantiate Platform and make methods static.

runtime/bin/process_impl.dart

Index: runtime/bin/process_impl.dart
diff --git a/runtime/bin/process_impl.dart b/runtime/bin/process_impl.dart
index 3811091c2264c20acb4c9194c238c102388b345a..1ff6de99539345007a73cb90a160aaaf6da46bd0 100644
--- a/runtime/bin/process_impl.dart
+++ b/runtime/bin/process_impl.dart
@@ -55,7 +55,7 @@ class _InteractiveProcess implements Process {
         throw new IllegalArgumentException("Non-string argument: $arg");
       }
       _arguments[i] = arguments[i];
-      if (new Platform().operatingSystem() == 'windows') {
+      if (Platform.operatingSystem() == 'windows') {
         _arguments[i] = _windowsArgumentEscape(_arguments[i]);
       }
     }