Fix static warnings spotted by dartc.

sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(revision 23012)
+++ sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(working copy)
@@ -771,8 +771,8 @@
     element = element.implementation;
     if (isNativeElement(element) && element.isField()) {
       var type = typeOf.putIfAbsent(element, () {
-        InterfaceType type = element.computeType(compiler).asRaw();
-        return type.isDynamic ? dynamicType : new TypeMask.subtype(type);
+        InterfaceType rawType = element.computeType(compiler).asRaw();
+        return rawType.isDynamic ? dynamicType : new TypeMask.subtype(rawType);
       });
       assert(type != null);
       return type;