Add feature and flag to enable incognito Chrome Custom Tabs

kCCTIncognito feature and flag are added to enable/disable incognito
Chrome Custom Tabs. The default is set to disabled.

Bug: 1023759
Change-Id: If32d256e3e9eaa94bcc09f7538c85e2dab53c589
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1911201
Reviewed-by: Peter Conn <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Commit-Queue: Ramin Halavati <[email protected]>
Cr-Commit-Position: refs/heads/master@{#714849}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index a85e9e1..d1c2cd0 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1405,6 +1405,9 @@
 extern const char kBackgroundTaskComponentUpdateName[];
 extern const char kBackgroundTaskComponentUpdateDescription[];
 
+extern const char kCCTIncognitoName[];
+extern const char kCCTIncognitoDescription[];
+
 extern const char kCCTModuleName[];
 extern const char kCCTModuleDescription[];