Fixed crash if tab closes while WebShare picker dialog is open.

chrome/browser/webshare/share_service_impl.h

 // 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.
 
 #ifndef CHROME_BROWSER_WEBSHARE_SHARE_SERVICE_IMPL_H_
 #define CHROME_BROWSER_WEBSHARE_SHARE_SERVICE_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
+#include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "third_party/WebKit/public/platform/modules/webshare/webshare.mojom.h"
 #include "third_party/WebKit/public/platform/site_engagement.mojom.h"
 
 class DictionaryValue;
 class GURL;
 
@@ skipping 59 matching lines @@
                                   const GURL& share_url,
                                   std::string* url_template_filled);
 
   void OnPickerClosed(std::unique_ptr<base::DictionaryValue> share_targets,
                       const std::string& title,
                       const std::string& text,
                       const GURL& share_url,
                       const ShareCallback& callback,
                       base::Optional<std::string> result);
 
+  base::WeakPtrFactory<ShareServiceImpl> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ShareServiceImpl);
 };
 
 #endif  // CHROME_BROWSER_WEBSHARE_SHARE_SERVICE_IMPL_H_