Add a pref name for share targets, and store their manifest data.

chrome/browser/webshare/share_target_pref_helper.h

Index: chrome/browser/webshare/share_target_pref_helper.h
diff --git a/chrome/browser/webshare/share_target_pref_helper.h b/chrome/browser/webshare/share_target_pref_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..511564a22f90c99dfb32a66c98d30125335668bf
--- /dev/null
+++ b/chrome/browser/webshare/share_target_pref_helper.h
@@ -0,0 +1,21 @@
+// Copyright 2017 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_TARGET_PREF_HELPER_H_
+#define CHROME_BROWSER_WEBSHARE_SHARE_TARGET_PREF_HELPER_H_
+
+#include "base/optional.h"
+#include "base/strings/string_piece.h"
+
+class PrefService;
+
+// Adds the Web Share target |share_target_origin| with template |url_template|
+// to |pref_service| under kWebShareVisitedTargets. If |url_template| is null,
+// this function will remove |share_target_origin| from kWebShareVisitedTargets,
+// if it is there.
+void UpdateShareTargetInPrefs(base::StringPiece manifest_url,
+                           base::Optional<std::string> url_template,
+                           PrefService* pref_service);
+
+#endif // CHROME_BROWSER_WEBSHARE_SHARE_TARGET_PREF_HELPER_H_