Move relevent JS tests to mojo_js_unittests

mojo/bindings/js/core_unittests.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 define([
     "gin/test/expect",
     "mojo/bindings/js/core",
   ], function(expect, core) {
   runWithPipe(testNop);
   runWithPipe(testReadAndWriteMessage);
@@ skipping 30 matching lines @@
 
     expect(read.result).toBe(core.RESULT_OK);
     expect(read.buffer.byteLength).toBe(42);
     expect(read.handles.length).toBe(0);
 
     var memory = new Uint8Array(read.buffer);
     for (var i = 0; i < memory.length; ++i)
       expect(memory[i]).toBe((i * i) & 0xFF);
   }
 });