Do not apply optimizations based on an element if that element cannot be resolved.

tests/compiler/dart2js/value_range_test.dart

 // Copyright (c) 2012, 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 'compiler_helper.dart';
 
 const int REMOVED = 0;
 const int ABOVE_ZERO = 1;
 const int BELOW_LENGTH = 2;
 const int KEPT = 3;
@@ skipping 203 matching lines @@
   class List {
     List();
     List.fixedLength(length);
   }
   abstract class Map {}
   class Closure {}
   class Null {}
   class Dynamic_ {}
   bool identical(Object a, Object b) {}''';
 
+const String INTERCEPTORSLIB_WITH_MEMBERS = r'''
+  class JSArray {
+    var length;
+    var removeLast;
+    operator[] (_) {}
+  }
+  class JSString {
+    var length;
+  }
+  class JSNumber {
+  }
+  class JSInt {
+  }
+  class JSDouble {
+  }
+  class JSNull {
+  }
+  class JSBool {
+  }
+  class JSFunction {
+  }
+  class ObjectInterceptor {
+  }
+  getInterceptor(x) {}''';
+
 expect(String code, int kind) {
-  String generated =
-      compile(code, coreSource: DEFAULT_CORELIB_WITH_LIST_INTERFACE);
+  String generated = compile(
+      code,
+      coreSource: DEFAULT_CORELIB_WITH_LIST_INTERFACE,
+      interceptorsSource: INTERCEPTORSLIB_WITH_MEMBERS);
   switch (kind) {
     case REMOVED:
       Expect.isTrue(!generated.contains('ioore'));
       break;
 
     case ABOVE_ZERO:
       Expect.isTrue(!generated.contains('< 0'));
       Expect.isTrue(generated.contains('ioore'));
       Expect.isTrue(generated.contains('ioore'));
       break;
@@ skipping 20 matching lines @@
       break;
   }
 }
 
 
 main() {
   for (int i = 0; i < TESTS.length;  i += 2) {
     expect(TESTS[i], TESTS[i + 1]);
   }
 }