[LayoutNG] Add a chrome:://flags for LayoutNG

This is to allow easy user-testing.

Bug: 591099
Change-Id: Ib08bbe1144b27c0fa37de9a12be9d4d21d00f52e
Reviewed-on: https://chromium-review.googlesource.com/1124138
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Emil A Eklund <[email protected]>
Reviewed-by: Dmitry Gozman <[email protected]>
Commit-Queue: Ian Kilpatrick <[email protected]>
Cr-Commit-Position: refs/heads/master@{#572466}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 3a00ba5..5ec8d3a 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -350,6 +350,9 @@
 extern const char kLayeredAPIName[];
 extern const char kLayeredAPIDescription[];
 
+extern const char kEnableLayoutNGName[];
+extern const char kEnableLayoutNGDescription[];
+
 extern const char kEnableLazyFrameLoadingName[];
 extern const char kEnableLazyFrameLoadingDescription[];