[SendTabToSelfHistory] Add a feature flag for history

Adding send_tab_to_self::kSendTabToSelfHistory  which will gate
near-term-experimental work for enabling a user flow to revisit
shared tabs.

Bug: 961913
Change-Id: I5365816dfc1c2fe6f05931c30386052f63e4ce61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610219
Commit-Queue: Jeffrey Cohen <[email protected]>
Reviewed-by: Peter Lee <[email protected]>
Reviewed-by: sebsg <[email protected]>
Cr-Commit-Position: refs/heads/master@{#659520}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index bfbcbac..3be23a6d 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -954,11 +954,14 @@
 extern const char kScrollableTabStripName[];
 extern const char kScrollableTabStripDescription[];
 
+extern const char kSendTabToSelfName[];
+extern const char kSendTabToSelfDescription[];
+
 extern const char kSendTabToSelfBroadcastName[];
 extern const char kSendTabToSelfBroadcastDescription[];
 
-extern const char kSendTabToSelfName[];
-extern const char kSendTabToSelfDescription[];
+extern const char kSendTabToSelfHistoryName[];
+extern const char kSendTabToSelfHistoryDescription[];
 
 extern const char kSendTabToSelfShowSendingUIName[];
 extern const char kSendTabToSelfShowSendingUIDescription[];