Copy dart2js source into pkg/compiler

pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.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.
 
 part of ssa;
 
 /**
  * [InvokeDynamicSpecializer] and its subclasses are helpers to
  * optimize intercepted dynamic calls. It knows what input types
  * would be beneficial for performance, and how to change a invoke
@@ skipping 708 matching lines @@
   }
 
   HInstruction newBuiltinVariant(HInvokeDynamic instruction,
                                  Compiler compiler) {
     JavaScriptBackend backend = compiler.backend;
     return new HLessEqual(
         instruction.inputs[1], instruction.inputs[2],
         instruction.selector, backend.boolType);
   }
 }