[ntp][modules] Adds module registration system and dummy module

The dummy module helps us build out the module infrastructure. This CL
adds the dummy module plus a few management functions to register and
render modules.

+ Add feature flag to enable NTP modules.

Fixed: 1110055
Change-Id: Iea63854a82bc9facacb7f75aad2d26f629e60e9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2333526
Auto-Submit: Tibor Goldschwendt <[email protected]>
Reviewed-by: Moe Ahmadi <[email protected]>
Commit-Queue: Tibor Goldschwendt <[email protected]>
Cr-Commit-Position: refs/heads/master@{#794658}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 5719c9d2..900d203 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1806,6 +1806,9 @@
 extern const char kNtpWebUIName[];
 extern const char kNtpWebUIDescription[];
 
+extern const char kNtpModulesName[];
+extern const char kNtpModulesDescription[];
+
 extern const char kEnableReaderModeName[];
 extern const char kEnableReaderModeDescription[];