code: function modifiersPressed(names) {
  
          // If any required modifiers are not pressed, return false
          for (var i=0; i < names.length; i++) {
  
              // Test whether current modifier is pressed
              var name = names[i];
              if (!(name in modifierKeysyms))
                  return false;
  
          }
  
          // Otherwise, all required modifiers are pressed
          return true;
  
      }
docs: Returns whether all modifiers having the given names are currently
  active.
  
  @private
  @param {String[]} names
  The names of all modifiers to test.
  
  @returns {Boolean}
  true if all specified modifiers are pressed, false otherwise.