Remove an unused optimization that does unsound conversion of

    var o = { prop : function() {} };
to
    var o = { prop() {} };

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128376960

src/com/google/javascript/jscomp/DefaultPassConfig.java

@@ -828,7 +828,6 @@ protected List<PassFactory> getOptimizations() {
     // Raise to ES6, if allowed
     if (options.getLanguageOut().isEs6OrHigher()) {
       passes.add(optimizeToEs6);
-      passes.add(objectLitAssignmentShortening);
       passes.add(rewriteBindThis);
     }
 
@@ -2710,14 +2709,6 @@ protected CompilerPass create(AbstractCompiler compiler) {
     }
   };
 
-  private final PassFactory objectLitAssignmentShortening =
-      new PassFactory("objectLitAssignmentShortening", true) {
-    @Override
-    protected CompilerPass create(AbstractCompiler compiler) {
-      return new ObjectLitAssignmentShortening(compiler);
-    }
-  };
-
   private final PassFactory rewriteBindThis =
       new PassFactory("rewriteBindThis", true) {
     @Override