Added Web Share (navigator.share) experimental web API (stub).

third_party/WebKit/public/platform/modules/webshare/webshare.mojom

Index: third_party/WebKit/public/platform/modules/webshare/webshare.mojom
diff --git a/third_party/WebKit/public/platform/modules/webshare/webshare.mojom b/third_party/WebKit/public/platform/modules/webshare/webshare.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..5291919be8d5c30ec5f33e42684400a30c702993
--- /dev/null
+++ b/third_party/WebKit/public/platform/modules/webshare/webshare.mojom
@@ -0,0 +1,11 @@
+// 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.
+
+module blink.mojom;
+
+interface ShareService {
+  // The web contents has requested to send a share text action. Returns null on
+  // success, or an error message on failure.
+  Share(string title, string text) => (string? error);
+};