Compute the script Uri lazily

runtime/lib/internal_patch.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:core' hide Symbol;
 import 'dart:typed_data' show Int32List;
 
 @patch
 List makeListFixedLength(List growableList)
     native "Internal_makeListFixedLength";
@@ skipping 16 matching lines @@
   // Implementation of Resource.readAsBytes.
   static var resourceReadAsBytes;
 
   // Implementation of package root/map provision.
   static var packageRootString;
   static var packageConfigString;
   static var packageRootUriFuture;
   static var packageConfigUriFuture;
   static var resolvePackageUriFuture;
 
-  static var platformScript;
+  static var _computeScriptUri;
+  static var _cachedScript;
+  static set platformScript(var f) {
+    _computeScriptUri = f;
+    _cachedScript = null;
+  }
+
+  static get platformScript {
+    if (_cachedScript == null && _computeScriptUri != null) {
+      _cachedScript = _computeScriptUri();
+    }
+    return _cachedScript;
+  }
 }
 
 final bool is64Bit = _inquireIs64Bit();
 
 bool _inquireIs64Bit() native "Internal_inquireIs64Bit";
 
 bool _classRangeCheck(int cid, int lowerLimit, int upperLimit) {
   return cid >= lowerLimit && cid <= upperLimit;
 }
 
@@ skipping 25 matching lines @@
     native "Internal_prependTypeArguments";
 
 // Called by IRRegExpMacroAssembler::GrowStack.
 Int32List _growRegExpStack(Int32List stack) {
   final newStack = new Int32List(stack.length * 2);
   for (int i = 0; i < stack.length; i++) {
     newStack[i] = stack[i];
   }
   return newStack;
 }