Mojo C++ bindings: support mapping mojo string to WTF::String.

mojo/public/cpp/bindings/tests/wtf_test_base.cc

+// Copyright 2016 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.
+
+#include "mojo/public/cpp/bindings/tests/wtf_test_base.h"
+
+#include "third_party/WebKit/Source/wtf/CurrentTime.h"
+#include "third_party/WebKit/Source/wtf/MainThread.h"
+#include "third_party/WebKit/Source/wtf/Partitions.h"
+#include "third_party/WebKit/Source/wtf/WTF.h"
+
+namespace mojo {
+namespace test {
+namespace {
+
+double DummyGetCurrentTime() {
+  return 0.0;
+}
+
+bool g_wtf_initialized = false;
+
+}  // namespace
+
+WTFTestBase::~WTFTestBase() {}
+
+WTFTestBase::WTFTestBase() {}
+
+void WTFTestBase::SetUp() {
+  if (g_wtf_initialized)
+    return;
+
+  WTF::Partitions::initialize(nullptr);
+  WTF::setTimeFunctionsForTesting(DummyGetCurrentTime);
+  WTF::initialize(nullptr);
+  WTF::initializeMainThread(0);
+  g_wtf_initialized = true;

[haraken, 2016/03/07 23:54:17]

Can we use blink::initializeWithoutV8/shutdownWithoutV8?

The reason I want to avoid directly calling WTF:: functions is that they are not
public APIs. It is a layering violation :/

[yzshen1, 2016/03/08 00:17:09]

I tried it, but that requires to link against the "web" target which is way
bigger than wtf. :/
IMO, this is a test class that tests exactly WTF stuff. It doesn't seem too bad
to use WTF initialization directly. WDYT? Thanks!

[haraken, 2016/03/08 00:29:29]

Then can we add a public API (in public/platform/) to initialize only WTF and
platform? (assuming it's acceptable to link against the wtf and platform
target.)

+}
+
+}  // namespace test
+}  // namespace mojo