Add Quota.TimeSinceOriginEvicted UMA histogram.

storage/browser/quota/quota_database.h

Index: storage/browser/quota/quota_database.h
diff --git a/storage/browser/quota/quota_database.h b/storage/browser/quota/quota_database.h
index 02a76fc09853a3e23fb14eb6554ff28149481a1f..09e90b34bfeb4e28157144fae2dc5999f2240605 100644
--- a/storage/browser/quota/quota_database.h
+++ b/storage/browser/quota/quota_database.h
@@ -58,6 +58,14 @@ class STORAGE_EXPORT_PRIVATE QuotaDatabase {
                                  StorageType type,
                                  base::Time last_modified_time);
 
+  bool GetOriginLastEvictionTime(const GURL& origin,
+                                 StorageType type,
+                                 base::Time* last_eviction_time);
+  bool SetOriginLastEvictionTime(const GURL& origin,
+                                 StorageType type,
+                                 base::Time last_eviction_time);
+  bool DeleteOriginLastEvictionTime(const GURL& origin, StorageType type);
+
   // Register initial |origins| info |type| to the database.
   // This method is assumed to be called only after the installation or
   // the database schema reset.