Google Inc. co-founders Larry Page and Sergey Brin have added almost $4 billion to their individual fortunes today as shares of the Internet search giant surge as much as 15 percent. Ruth Porat, who joined Google in May, yesterday signaled plans to bring more restraint to spending as the Mountain View, California-based company reported profit that exceeded analyst estimates. The fortunes of Page and Brin are up more than 20 percent this year, an increase of almost $7 billion each, according to the Bloomberg Billionaires Index.