Implement the new polling system in the BackgroundFetchJobController

content/browser/background_fetch/background_fetch_constants.h

Index: content/browser/background_fetch/background_fetch_constants.h
diff --git a/content/browser/background_fetch/background_fetch_constants.h b/content/browser/background_fetch/background_fetch_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..cb6c42f9939d33180c8e5ec178d9416668374508
--- /dev/null
+++ b/content/browser/background_fetch/background_fetch_constants.h
@@ -0,0 +1,18 @@
+// 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 CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_CONSTANTS_H_
+#define CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_CONSTANTS_H_
+
+namespace content {
+
+// Maximum number of parallel requests that a Background Fetch should fetch.
+constexpr size_t kMaximumBackgroundFetchParallelRequests = 1;
+
+// Value used to refer to an invalid request index for Background Fetch.
+constexpr int kInvalidBackgroundFetchRequestIndex = -1;
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_CONSTANTS_H_