code: function isPotentiallyFocusable(element) {
      // Inputs are potentially focusable *unless* they're type="hidden".
      if (isHiddenInput(element)) {
          return false;
      }
      return isNativeFormElement(element) ||
          isAnchorWithHref(element) ||
          element.hasAttribute('contenteditable') ||
          hasValidTabIndex(element);
  }
docs: Gets whether an element is potentially focusable without taking current visible/disabled state
  into account.
  @param {?} element
  @return {?}