Implemented stub ShareService mojo service, for navigator.share.

chrome/browser/webshare/share_service_impl.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 "chrome/browser/webshare/share_service_impl.h"
+
+ShareServiceImpl::ShareServiceImpl(blink::mojom::ShareServiceRequest request)
+    : binding_(this) {
+  binding_.Bind(std::move(request));
+}
+
+ShareServiceImpl::~ShareServiceImpl() {}
+
+// static
+void ShareServiceImpl::Create(mojo::InterfaceRequest<ShareService> request) {
+  new ShareServiceImpl(std::move(request));
+}
+
+void ShareServiceImpl::Share(const std::string& title,
+                             const std::string& text,
+                             const GURL& url,
+                             const ShareCallback& callback) {
+  // TODO(constantina@): implement Web Share Target here.
+  NOTIMPLEMENTED();
+  callback.Run(base::Optional<std::string>("Not implemented: navigator.share"));
+}