Fix bug http://code.google.com/p/dart/issues/detail?id=12941 by doing speculative optimizations eve…

sdk/lib/_internal/compiler/implementation/ssa/bailout.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 ssa;
 
 class BailoutInfo {
   int instructionId;
   int bailoutId;
   BailoutInfo(this.instructionId, this.bailoutId);
@@ skipping 105 matching lines @@
   bool get hasTypeGuards => work.guards.length != 0;
 
   bool isUsedWithIncompatibleSelector(HInstruction instruction,
                                       HType speculativeType) {
     for (HInstruction user in instruction.usedBy) {
       if (user is HCheck
           && isUsedWithIncompatibleSelector(user, speculativeType)) {
         return true;
       } else if (user.selector != null
                  && user.getDartReceiver(compiler) == instruction
-                 && !speculativeType.computeMask(compiler).willHit(
+                 && !speculativeType.computeMask(compiler).understands(
                         user.selector, compiler)) {
         return true;
       }
     }
     return false;
   }
 
   bool typeGuardWouldBeValuable(HInstruction instruction,
                                 HType speculativeType) {
     // If the type itself is not valuable, do not generate a guard for it.
@@ skipping 563 matching lines @@
         hasComplexBailoutTargets = true;
       }
     } else {
       hasComplexBailoutTargets = true;
       blocks.forEach((HBasicBlock block) {
         block.bailoutTargets.add(target);
       });
     }
   }
 }