[wasm] Implement parallel compilation.

test/mjsunit/wasm/wasm-module-builder.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function WasmFunctionBuilder(name, sig_index) {
     this.name = name;
     this.sig_index = sig_index;
     this.exports = [];
 }
 
@@ skipping 324 matching lines @@
 }
 
 WasmModuleBuilder.prototype.instantiate = function(ffi, memory) {
     var buffer = this.toBuffer();
     if (memory != undefined) {
       return Wasm.instantiateModule(buffer, ffi, memory);
     } else {
       return Wasm.instantiateModule(buffer, ffi);
     }
 }
+
+function assertModule(module, memsize) {
+  // Check the module exists.
+  assertFalse(module === undefined);
+  assertFalse(module === null);
+  assertFalse(module === 0);
+  assertEquals("object", typeof module);
+
+  // Check the memory is an ArrayBuffer.
+  var mem = module.exports.memory;
+  assertFalse(mem === undefined);
+  assertFalse(mem === null);
+  assertFalse(mem === 0);
+  assertEquals("object", typeof mem);
+  assertTrue(mem instanceof ArrayBuffer);
+  for (var i = 0; i < 4; i++) {
+    module.exports.memory = 0;  // should be ignored
+    assertEquals(mem, module.exports.memory);
+  }
+
+  assertEquals(memsize, module.exports.memory.byteLength);
+}
+
+function assertFunction(module, func) {
+  assertEquals("object", typeof module.exports);
+
+  var exp = module.exports[func];
+  assertFalse(exp === undefined);
+  assertFalse(exp === null);
+  assertFalse(exp === 0);
+  assertEquals("function", typeof exp);
+  return exp;
+}