Rename "parallel recompilation" to "concurrent recompilation".

test/mjsunit/mjsunit.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 82 matching lines @@
 var assertDoesNotThrow;
 
 // Asserts that the found value is an instance of the constructor passed
 // as the second argument.
 var assertInstanceof;
 
 // Assert that this code is never executed (i.e., always fails if executed).
 var assertUnreachable;
 
 // Assert that the function code is (not) optimized.  If "no sync" is passed
-// as second argument, we do not wait for the parallel optimization thread to
+// as second argument, we do not wait for the concurrent optimization thread to
 // finish when polling for optimization status.
 // Only works with --allow-natives-syntax.
 var assertOptimized;
 var assertUnoptimized;
 
 
 (function () {  // Scope for utility functions.
 
   function classOf(object) {
     // Argument must not be null or undefined.
@@ skipping 263 matching lines @@
     assertTrue(OptimizationStatus(fun, sync_opt) != 1, name_opt);
   }
 
   assertOptimized = function assertOptimized(fun, sync_opt, name_opt) {
     if (sync_opt === undefined) sync_opt = "";
     assertTrue(OptimizationStatus(fun, sync_opt) != 2, name_opt);
   }
 
 })();