Make history expiration more aggressive.

chrome/browser/history/expire_history_backend.cc

Index: chrome/browser/history/expire_history_backend.cc
===================================================================
--- chrome/browser/history/expire_history_backend.cc	(revision 107144)
+++ chrome/browser/history/expire_history_backend.cc	(working copy)
@@ -29,7 +29,17 @@
 
 // The number of days by which the expiration threshold is advanced for items
 // that we want to expire early, such as those of AUTO_SUBFRAME transition type.
-const int kEarlyExpirationAdvanceDays = 30;
+//
+// Early expiration stuff is kept around only for edge cases, as subframes
+// don't appear in history and the vast majority of them are ads anyway. The
+// main use case for these is if you're on a site with links to different
+// frames, you'll be able to see those links as visited, and we'll also be
+// able to get redirect information for those URLs.
+//
+// But since these uses are most valuable when you're actually on the site,
+// and because these can take up the bulk of your history, we get a lot of
+// space savings by deleting them quickly.
+const int kEarlyExpirationAdvanceDays = 3;
 
 // Reads all types of visits starting from beginning of time to the given end
 // time. This is the most general reader.
@@ -111,7 +121,7 @@
 
 // The number of visits we will expire very time we check for old items. This
 // Prevents us from doing too much work any given time.
-const int kNumExpirePerIteration = 10;
+const int kNumExpirePerIteration = 32;
 
 // The number of seconds between checking for items that should be expired when
 // we think there might be more items to expire. This timeout is used when the
@@ -131,7 +141,7 @@
 
 // The number of the most recent months for which we do not want to delete
 // the history index files.
-const int kStoreHistoryIndexesForMonths = 12;
+const int kStoreHistoryIndexesForMonths = 3;
 
 }  // namespace