Allow constexpr variables of TimeDelta type.

components/offline_pages/offline_page_model.cc

Index: components/offline_pages/offline_page_model.cc
diff --git a/components/offline_pages/offline_page_model.cc b/components/offline_pages/offline_page_model.cc
index 3472066eb9fa33f5dfd6b8b1633e85fee0041ffa..2e935e0ae0ba21a74cd0e89e3ea2196656f665a0 100644
--- a/components/offline_pages/offline_page_model.cc
+++ b/components/offline_pages/offline_page_model.cc
@@ -41,10 +41,6 @@ enum ClearAllStatus {
   CLEAR_ALL_STATUS_COUNT
 };
 
-// Threshold for how old offline copy of a page should be before we offer to
-// delete it to free up space.
-const base::TimeDelta kPageCleanUpThreshold = base::TimeDelta::FromDays(30);
-
 // The maximum histogram size for the metrics that measure time between views of
 // a given page.
 const base::TimeDelta kMaxOpenedPageHistogramBucket =