Reapply change to update dart2js operator equals semantics to follow

lib/compiler/implementation/ssa/builder.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.
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 79 matching lines @@
   }
 
   Element getIndexInterceptor() {
     return compiler.findHelper(const SourceString('index'));
   }
 
   Element getIndexAssignmentInterceptor() {
     return compiler.findHelper(const SourceString('indexSet'));
   }
 
-  Element getEqualsNullInterceptor() {
-    return compiler.findHelper(const SourceString('eqNull'));
-  }
-
   Element getExceptionUnwrapper() {
     return compiler.findHelper(const SourceString('unwrapException'));
   }
 
   Element getClosureConverter() {
     return compiler.findHelper(const SourceString('convertDartClosureToJS'));
   }
 
   Element getTraceFromException() {
     return compiler.findHelper(const SourceString('getTraceFromException'));
@@ skipping 3429 matching lines @@
             new HSubGraphBlockInformation(thenGraph),
             new HSubGraphBlockInformation(elseGraph));
 
     HBasicBlock conditionStartBlock = conditionGraph.start;
     conditionGraph.start.setBlockFlow(info, joinBlock);
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }