Add IDL and initial Blink API for Background Sync

Source/modules/background_sync/SyncRegistrationOptions.idl

Index: Source/modules/background_sync/SyncRegistrationOptions.idl
diff --git a/Source/modules/encryptedmedia/MediaKeyStatusMap.idl b/Source/modules/background_sync/SyncRegistrationOptions.idl
similarity index 35%
copy from Source/modules/encryptedmedia/MediaKeyStatusMap.idl
copy to Source/modules/background_sync/SyncRegistrationOptions.idl
index f0775839f6bfcf65a1909be51f43114cb5a642c5..795b2dd1f838e80a0b4a26e76f00e211dd909ff5 100644
--- a/Source/modules/encryptedmedia/MediaKeyStatusMap.idl
+++ b/Source/modules/background_sync/SyncRegistrationOptions.idl
@@ -2,18 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://w3c.github.io/encrypted-media/#idl-def-MediaKeyStatusMap
-
-enum MediaKeyStatus {
-    "usable",
-    "expired",
-    "output-not-allowed",
-    "internal-error"
+enum SyncNetworkType {
+  "network-any",
+  "network-offline",
+  "network-online",
+  "network-non-mobile",
 };
 
 [
-    GarbageCollected,
-] interface MediaKeyStatusMap {
-    readonly attribute unsigned long size;
-    readonly maplike <BufferSource, MediaKeyStatus>;
+    RuntimeEnabled=BackgroundSync,
+] dictionary SyncRegistrationOptions {
+    SyncNetworkType minRequiredNetwork = "network-online";
+    boolean allowOnBattery = true;
+    boolean idleRequired = false;
 };