[Contextual Search] Change "Now on Tap" to "Contextual Cards"

BUG=644934

Review-Url: https://codereview.chromium.org/2361163003
Cr-Commit-Position: refs/heads/master@{#420899}
  void recordSurroundingText(const std::string& after_text) {
    after_text_ = after_text;
  }

  void recordSurroundingText(const std::string& after_text) {
    after_text_ = after_text;
  }
