Rename Download Glue Implementation

> Implemented glue between UI side and native side code on both download manager path
and offline item path
> Defined API on native side for download item to excute rename
> Added DownloadRename chrome feature flag

Change-Id: I558713c37479bd0ebbf93f723e98278204580e0a
Bug: 924751
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1484617
Reviewed-by: Carlos Knippschild <[email protected]>
Reviewed-by: Elly Fong-Jones <[email protected]>
Reviewed-by: Peter Beverloo <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Commit-Queue: Hesen Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#640146}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 612aa6c..16efae1 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1361,6 +1361,9 @@
 extern const char kDownloadHomeV2Name[];
 extern const char kDownloadHomeV2Description[];
 
+extern const char kDownloadRenameName[];
+extern const char kDownloadRenameDescription[];
+
 extern const char kAutofillManualFallbackAndroidName[];
 extern const char kAutofillManualFallbackAndroidDescription[];