[epiphany] Fix theoretical race condition in ephy_history_service_add_visit_row

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 2237adc1c7519d1565291a5080da3fbbdb99e669
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Mon Feb 20 20:24:03 2017 -0600

    Fix theoretical race condition in ephy_history_service_add_visit_row
    
    The design of the history service feels like one big footgun. I'm really
    not sure why a history thread is necessary at all, or why we have
    longstanding transactions (defeating the entire purpose of transactions)
    instead of just using autocommit, which I think would be sufficient for
    everything we do.
    
    This commit doesn't fix any of that. That's just a rant. This commit
    just fixes one theoretical race condition. Prepared statements lock the
    database and need to be finalized BEFORE commit. The current code only
    works if the prepared statement is finalized on the UI thread before the
    scheduled commit occurs on the history thread. Which is probably always,
    but let's not leave it to luck.
    
    I could see this leading to a small loss of the last bit of history when
    closing the browser.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=778649

 lib/history/ephy-history-service-visits-table.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/lib/history/ephy-history-service-visits-table.c b/lib/history/ephy-history-service-visits-table.c
index 2e1ff53..b13ae3f 100644
--- a/lib/history/ephy-history-service-visits-table.c
+++ b/lib/history/ephy-history-service-visits-table.c
@@ -84,8 +84,12 @@ ephy_history_service_add_visit_row (EphyHistoryService *self, EphyHistoryPageVis
     visit->id = ephy_sqlite_connection_get_last_insert_id (self->history_database);
   }
 
-  ephy_history_service_schedule_commit (self);
+  /* Remember kids: prepared statements lock the database! They must be unreffed
+   * before scheduling commit.
+   */
   g_object_unref (statement);
+
+  ephy_history_service_schedule_commit (self);
 }
 
 static EphyHistoryPageVisit *