Bug 452836 - Optimize calls to sqlite3_prepare_v2

This makes sqlite not copy the sql string when preparing it, saving us a string
copy every time.
r=bholley

storage/src/mozStorageStatement.cpp

@@ -114,8 +114,11 @@ mozStorageStatement::Initialize(mozStorageConnection *aDBConnection,
     NS_ENSURE_TRUE(db != nsnull, NS_ERROR_NULL_POINTER);
 
     int srv;
-    srv = sqlite3_prepare_v2(db, nsPromiseFlatCString(aSQLStatement).get(),
-                             aSQLStatement.Length(), &mDBStatement, NULL);
+    // We pass Length() + 1 to sqlite because it checks if the sql string it is
+    // given contains '\0' at the specified length.  If it does contain '\0', it
+    // will not copy the string.
+    srv = sqlite3_prepare_v2(db, PromiseFlatCString(aSQLStatement).get(),
+                             aSQLStatement.Length() + 1, &mDBStatement, NULL);
     if (srv != SQLITE_OK) {
 #ifdef PR_LOGGING
         PR_LOG(gStorageLog, PR_LOG_ERROR, ("Sqlite statement prepare error: %d '%s'", srv, sqlite3_errmsg(db)));