dart2js cps: Introduce '<<' operator in type propagation.

pkg/compiler/lib/src/cps_ir/builtin_operator.dart

 // Copyright (c) 2015, 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.
 library builtin_operator;
 // This is shared by the CPS and Tree IRs.
 // Both cps_ir_nodes and tree_ir_nodes import and re-export this file.
 
 /// An operator supported natively in the CPS and Tree IRs using the
 /// `ApplyBuiltinOperator` instructions.
 ///
@@ skipping 14 matching lines @@
 enum BuiltinOperator {
   /// The numeric binary operators must take two numbers as argument.
   /// The bitwise operators coerce the result to an unsigned integer, but
   /// otherwise these all behave like the corresponding JS operator.
   NumAdd,
   NumSubtract,
   NumMultiply,
   NumAnd,
   NumOr,
   NumXor,
+  NumShl,
   NumLt,
   NumLe,
   NumGt,
   NumGe,
 
   /// Concatenates any number of strings.
   ///
   /// Takes any number of arguments, and each argument must be a string.
   ///
   /// Returns the empty string if no arguments are given.
@@ skipping 51 matching lines @@
   /// Compiles to `Math.floor(x) === x`
   IsFloor,
 
   /// Returns true if the argument is an integer.
   ///
   /// The argument must be repeated 3 times.
   ///
   /// Compiles to `typeof x === 'number' && Math.floor(x) === x`
   IsNumberAndFloor,
 }