message: Add IfThisThenThat Lint to KeyEvent.
  #codehealth
diff: @@ -58,6 +58,7 @@ enum CompositionMode {
  }
  message KeyEvent {
  + // LINT.IfChange
  enum SpecialKey {
  NO_SPECIALKEY = 0;
  DIGIT = 1;
  @@ -230,6 +231,11 @@ message KeyEvent {
  RIGHT_SHIFT = 1024;
  CAPS = 2048;
  }
  + // LINT.ThenChange(
  + // //composer/key_parser.cc,
  + // //gui/config_dialog/keybinding_editor.cc,
  + // //unix/ibus/key_translator.cc
  + // )
  // Probable key event, mainly for touch screen.
  // User's input has ambiguity (e.g. the touch position is merginal)
  