[Offline pages] Add feature flag for page renovation framework.

This feature flag will be used to enable and disable use of
renovations.

Design doc:
https://docs.google.com/a/google.com/document/d/1WuwRJaxBKAwVpeAHG0xhq5uRxMTB-j4LFleT4QEqANU

Bug: 736933
Change-Id: I2808e734a8a60e7b7eb45efc85b51299500018f4
Reviewed-on: https://chromium-review.googlesource.com/572664
Commit-Queue: Collin Baker <[email protected]>
Reviewed-by: Yafei Duan <[email protected]>
Reviewed-by: Peter Williamson <[email protected]>
Cr-Commit-Position: refs/heads/master@{#487998}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index fe4b11e7..e6311ba 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1061,6 +1061,9 @@
 extern const char kOfflinePagesPrefetchingName[];
 extern const char kOfflinePagesPrefetchingDescription[];
 
+extern const char kOfflinePagesRenovationsName[];
+extern const char kOfflinePagesRenovationsDescription[];
+
 extern const char kOfflinePagesSharingName[];
 extern const char kOfflinePagesSharingDescription[];