overview gesture: Add chrome flags for the feature.

Primarily for PM/UX testing. Currently it's still disabled by default.

Bug: 997885
Change-Id: Ic2c0c3792923631056de415b6b3f23b70500c605
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873289
Reviewed-by: Min Chen <[email protected]>
Commit-Queue: Min Chen <[email protected]>
Commit-Queue: Xiaoqian Dai <[email protected]>
Cr-Commit-Position: refs/heads/master@{#708467}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index cd014f9..6c6b688 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1899,6 +1899,9 @@
 extern const char kArcVpnName[];
 extern const char kArcVpnDescription[];
 
+extern const char kAshDragWindowFromShelfName[];
+extern const char kAshDragWindowFromShelfDescription[];
+
 extern const char kAshEnableDisplayMoveWindowAccelsName[];
 extern const char kAshEnableDisplayMoveWindowAccelsDescription[];