Disable sqlite lookaside buffers by default.

sql/connection.h

Index: sql/connection.h
diff --git a/sql/connection.h b/sql/connection.h
index 049d7cf5b4e2f9715ffc4b7f67dd2e89dc367bff..21b3e13bbf58aa92c0e5369f3af9cb4b5aed425c 100644
--- a/sql/connection.h
+++ b/sql/connection.h
@@ -140,6 +140,16 @@ class SQL_EXPORT Connection {
   // This must be called before Open() to have an effect.
   void set_exclusive_locking() { exclusive_locking_ = true; }
 
+
+  // Call to have the database use the default lookaside buffer for small object
+  // allocations. The lookaside buffer is intended to provide a speed boost when
+  // running with slow malloc implementations. However, under typical use-cases
+  // in Chrome, it seem to have no negligible impact while costing 50KB per
+  // connection, therefore we disable it by default.
+  //
+  // This must be called before Open() to have an effect.
+  void set_enable_lookaside_buffer() { enable_lookaside_buffer_ = true; }
+

[Scott Hess - ex-Googler, 2013/06/04 16:35:21]

IMHO, this is either the right thing to do, or not the right thing to do, though
it's possible that the choice differs per-platform.  So exposing this seems like
it's asking for trouble.

[rmcilroy, 2013/06/04 17:05:38]

Done.

   // Set an error-handling callback.  On errors, the error number (and
   // statement, if available) will be passed to the callback.
   //
@@ -496,6 +506,7 @@ class SQL_EXPORT Connection {
   int page_size_;
   int cache_size_;
   bool exclusive_locking_;
+  bool enable_lookaside_buffer_;
 
   // All cached statements. Keeping a reference to these statements means that
   // they'll remain active.