Expose Physical Web metadata to native clients over JNI

components/physical_web/data_source/physical_web_data_source.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 "components/physical_web/data_source/physical_web_data_source.h"
+
+const char kPhysicalWebDescriptionKey[] = "description";
+const char kPhysicalWebDistanceEstimateKey[] = "distanceEstimate";
+const char kPhysicalWebGroupIdKey[] = "groupId";
+const char kPhysicalWebIconUrlKey[] = "icon";
+const char kPhysicalWebResolvedUrlKey[] = "resolvedUrl";
+const char kPhysicalWebScanTimestampKey[] = "scanTimestamp";
+const char kPhysicalWebScannedUrlKey[] = "scannedUrl";
+const char kPhysicalWebTitleKey[] = "title";