Google’s employees were shocked when they learned in March that the South Korean consumer electronics giant Samsung was considering replacing Google with Microsoft’s Bing as the default search engine on its devices. . . .Google’s reaction to the Samsung threat was "panic," according to internal messages reviewed by The New York Times. An estimated $3 billion in annual revenue was at stake with the Samsung contract. An additional $20 billion is tied to a similar Apple contract that will be up for renewal this year.