Enable sync for the settings from the Extension Settings API.

chrome/browser/sync/protocol/proto_value_conversions.h

Index: chrome/browser/sync/protocol/proto_value_conversions.h
diff --git a/chrome/browser/sync/protocol/proto_value_conversions.h b/chrome/browser/sync/protocol/proto_value_conversions.h
index e9da22c135ad863ae4242e67e1d207f95995dbff..5556d3fd978e1b9294635ec01d50bd8fbb0a1e33 100644
--- a/chrome/browser/sync/protocol/proto_value_conversions.h
+++ b/chrome/browser/sync/protocol/proto_value_conversions.h
@@ -19,6 +19,7 @@ class AutofillSpecifics;
 class BookmarkSpecifics;
 class EncryptedData;
 class EntitySpecifics;
+class ExtensionSettingSpecifics;
 class ExtensionSpecifics;
 class NigoriSpecifics;
 class PasswordSpecifics;
@@ -85,6 +86,9 @@ base::DictionaryValue* AutofillProfileSpecificsToValue(
 base::DictionaryValue* BookmarkSpecificsToValue(
     const sync_pb::BookmarkSpecifics& bookmark_specifics);
 
+base::DictionaryValue* ExtensionSettingSpecificsToValue(
+    const sync_pb::ExtensionSettingSpecifics& extension_setting_specifics);
+
 base::DictionaryValue* ExtensionSpecificsToValue(
     const sync_pb::ExtensionSpecifics& extension_specifics);