Move indexSet and unary operators to the new interceptor mechanism.

sdk/lib/_internal/compiler/implementation/js_backend/constant_system_javascript.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.
 
 part of js_backend;
 
 const JAVA_SCRIPT_CONSTANT_SYSTEM = const JavaScriptConstantSystem();
 
 class JavaScriptBitNotOperation extends BitNotOperation {
   const JavaScriptBitNotOperation();
@@ skipping 123 matching lines @@
     return result;
   }
 
   apply(left, right) => identical(left, right);
 }
 
 /**
  * Constant system following the semantics for Dart code that has been
  * compiled to JavaScript.
  */
-class JavaScriptConstantSystem implements ConstantSystem {
+class JavaScriptConstantSystem extends ConstantSystem {
   const int BITS31 = 0x8FFFFFFF;
   const int BITS32 = 0xFFFFFFFF;
   // The maximum integer value a double can represent without losing
   // precision.
   const int BITS53 = 0x1FFFFFFFFFFFFF;
 
   final add = const JavaScriptBinaryArithmeticOperation(const AddOperation());
   final bitAnd = const JavaScriptBinaryBitOperation(const BitAndOperation());
   final bitNot = const JavaScriptBitNotOperation();
   final bitOr = const JavaScriptBinaryBitOperation(const BitOrOperation());
@@ skipping 76 matching lines @@
     // At runtime, an integer is both an integer and a double: the
     // integer type check is Math.floor, which will return true only
     // for real integers, and our double type check is 'typeof number'
     // which will return true for both integers and doubles.
     if (s.element == compiler.intClass && t.element == compiler.doubleClass) {
       return true;
     }
     return compiler.types.isSubtype(s, t);
   }
 }