Video Tutorials : Set up feature flags and skeleton code directory

This CL sets up
- Video tutorials feature flag
- Video tutorials code directory in chrome/browser/video_tutorials/
- BUILD, DEPS, OWNERS files
- An empty VideoTutorialService class with factory

Bug: 1114065
Change-Id: I676ae7b8e83e3b2ff709d80a4f6ccdc96a316255
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2346742
Reviewed-by: Ted Choc <[email protected]>
Reviewed-by: Hesen Zhang <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Reviewed-by: Shakti Sahu <[email protected]>
Reviewed-by: ssid <[email protected]>
Reviewed-by: Theresa  <[email protected]>
Reviewed-by: Henrique Nakashima <[email protected]>
Commit-Queue: Shakti Sahu <[email protected]>
Cr-Commit-Position: refs/heads/master@{#798002}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index e5c8f12..98b1296 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1798,6 +1798,9 @@
 extern const char kUpdateNotificationServiceImmediateShowOptionName[];
 extern const char kUpdateNotificationServiceImmediateShowOptionDescription[];
 
+extern const char kVideoTutorialsName[];
+extern const char kVideoTutorialsDescription[];
+
 extern const char kPrefetchNotificationSchedulingIntegrationName[];
 extern const char kPrefetchNotificationSchedulingIntegrationDescription[];