[d8][wasm] Test wasm compilation completion

d8 was recently changed to keep running until wasm compilation has
completed. This adds a message test to test that.

R=ahaas@chromium.org

Change-Id: I73af53b6df4ee5f9a6afd26cf2d71a269140465f
Reviewed-on: https://chromium-review.googlesource.com/966184Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52008}

test/message/wasm-finish-compilation.js

+// Copyright 2018 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.
+
+// Flags: --no-stress-opt
+
+load('test/mjsunit/wasm/wasm-constants.js');
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+// Test that d8 does not terminate until wasm compilation has finished and the
+// promise was resolved.
+
+var builder = new WasmModuleBuilder();
+// Add a few functions so it takes some time to compile.
+for (var i = 0; i < 2000; ++i) {
+  builder.addFunction('fun' + i, kSig_i_v)
+      .addBody([...wasmI32Const(i)])
+      .exportFunc();
+}
+builder.asyncInstantiate()
+    .then(({module, instance}) => instance.exports.fun1155())
+    .then(res => print('Result of executing fun1155: ' + res));

test/message/wasm-finish-compilation.out

+Result of executing fun1155: 1155

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

@@ -683,6 +683,10 @@ class WasmModuleBuilder {
     return instance;
   }
 
+  asyncInstantiate(ffi) {
+    return WebAssembly.instantiate(this.toBuffer(), ffi);
+  }
+
   toModule(debug = false) {
     return new WebAssembly.Module(this.toBuffer(debug));
   }