Move InMemoryURLIndex Caching Operations to FILE Thread

chrome/browser/history/history_notifications.h

Index: chrome/browser/history/history_notifications.h
===================================================================
--- chrome/browser/history/history_notifications.h	(revision 117518)
+++ chrome/browser/history/history_notifications.h	(working copy)
@@ -25,7 +25,7 @@
   virtual ~HistoryDetails() {}
 };
 
-// Details for HISTORY_URL_VISITED.
+// Details for NOTIFICATION_HISTORY_URL_VISITED.
 struct URLVisitedDetails : public HistoryDetails {
   URLVisitedDetails();
   virtual ~URLVisitedDetails();
@@ -40,7 +40,7 @@
   history::RedirectList redirects;
 };
 
-// Details for NOTIFY_HISTORY_TYPED_URLS_MODIFIED.
+// Details for NOTIFICATION_HISTORY_TYPED_URLS_MODIFIED.
 struct URLsModifiedDetails : public HistoryDetails {
   URLsModifiedDetails();
   virtual ~URLsModifiedDetails();
@@ -49,7 +49,7 @@
   std::vector<URLRow> changed_urls;
 };
 
-// Details for NOTIFY_HISTORY_URLS_DELETED.
+// Details for NOTIFICATION_HISTORY_URLS_DELETED.
 struct URLsDeletedDetails : public HistoryDetails {
   URLsDeletedDetails();
   virtual ~URLsDeletedDetails();
@@ -57,9 +57,14 @@
   // Set when all history was deleted. False means just a subset was deleted.
   bool all_history;
 
+  // The URLRows which have been deleted.
+  std::vector<URLRow> rows;
+
   // The list of unique URLs affected. This is valid only when a subset of
   // history is deleted. When all of it is deleted, this will be empty, since
-  // we do not bother to list all URLs.
+  // we do not bother to list all URLs. (This information can be gleaned from
+  // |rows| but, since there are several clients who need the set, we pre-build
+  // it so that the clients don't have to.)
   std::set<GURL> urls;
 };