Add about://flags entry for tab scrolling.

Bug: 951078
Change-Id: Id66be9ff30e334f53338fa9848fa73db3ea318ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560373
Commit-Queue: Charlene Yan <[email protected]>
Reviewed-by: Taylor Bergquist <[email protected]>
Reviewed-by: Peter Kasting <[email protected]>
Cr-Commit-Position: refs/heads/master@{#650509}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 43d8ec9..b9c2c1a 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1030,6 +1030,9 @@
 extern const char kSaveasMenuLabelExperimentName[];
 extern const char kSaveasMenuLabelExperimentDescription[];
 
+extern const char kScrollableTabStripName[];
+extern const char kScrollableTabStripDescription[];
+
 extern const char kSendTabToSelfName[];
 extern const char kSendTabToSelfDescription[];