Changes to add duration into history database.

chrome/browser/history/history_types.h

Index: chrome/browser/history/history_types.h
diff --git a/chrome/browser/history/history_types.h b/chrome/browser/history/history_types.h
index 823a8369f98156ca606baeb602c6a5b7fb5c643c..3f618b0b097b9753fccc38c8106024cca5585761 100644
--- a/chrome/browser/history/history_types.h
+++ b/chrome/browser/history/history_types.h
@@ -197,6 +197,15 @@ typedef int64 VisitID;
 // Structure to hold the mapping between each visit's id and its source.
 typedef std::map<VisitID, VisitSource> VisitSourceMap;
 
+// The structure contains all the extra details about a visit stored
+// in visit_details database.Consider adding active_duration etc. in the future.
+struct VisitDetailRow {
+  base::TimeDelta duration;
+};

[GeorgeY, 2012/03/22 00:36:49]

We should not create extra tables when we have 1 to 1 relationship between them.
We should update the visits table as we do the migration anyway.

+
+// Structure to hold the mapping between each visit's id and its details.
+typedef std::map<VisitID, VisitDetailRow> VisitDetailMap;
+
 // VisitRow -------------------------------------------------------------------
 
 // Holds all information associated with a specific visit. A visit holds time
@@ -237,6 +246,12 @@ class VisitRow {
   // change.
   bool is_indexed;
 
+  // Record how much time a user has this visit starting from the user
+  // opened this visit to the user closed or ended this visit.
+  // This includes both active and inactive time as long as
+  // the visit was present.
+  base::Time visit_duration;

[GeorgeY, 2012/03/22 00:36:49]

This just reiterates my point: visit_duration is a part of the visit, makes
sense that it should be the part of the visit table as well.

For active_duration, on the other hand we could use a completely different
approach: have a table with |visit_id| and |time| and add to it every time user
switches tab/focus.

+
   // Compares two visits based on dates, for sorting.
   bool operator<(const VisitRow& other) {
     return visit_time < other.visit_time;