Revert "Improve hashCode for closure objects"

runtime/lib/function.dart

Index: runtime/lib/function.dart
diff --git a/runtime/lib/function.dart b/runtime/lib/function.dart
index c3b17d963b17a7ad94bec48f834ec37dae44c444..7f0556de37369ccc5dda11d71eea2b0e25f49832 100644
--- a/runtime/lib/function.dart
+++ b/runtime/lib/function.dart
@@ -5,23 +5,16 @@
 class _Closure implements Function {
   bool operator ==(other) native "Closure_equals";
 
-  int get hashCode {
-    if (_hash == null) {
-      _hash = _computeHash();
-    }
-    return _hash;
-  }
+  int get hashCode native "Closure_hashCode";
 
   _Closure get call => this;
 
   _Closure _clone() native "Closure_clone";
 
-  int _computeHash() native "Closure_computeHash";
-
   // No instance fields should be declared before the following 4 fields whose
   // offsets must be identical in Dart and C++.
 
-  // The following fields are declared both in raw_object.h (for direct access
+  // The following 4 fields are declared both in raw_object.h (for direct access
   // from C++ code) and also here so that the offset-to-field map used by
   // deferred objects is properly initialized.
   // Caution: These fields are not Dart instances, but VM objects. Their Dart
@@ -30,5 +23,4 @@ class _Closure implements Function {
   var _function_type_arguments;
   var _function;
   var _context;
-  var _hash;
 }