Fix Chrome search-cancel-button

[sagalbot]

.vs__search::-webkit-search-cancel-button {
  display: none;
}

The above CSS has always existed, but it was part of a grouping:

.vs__search::-webkit-search-decoration,
.vs__search::-webkit-search-cancel-button,
.vs__search::-webkit-search-results-button,
.vs__search::-webkit-search-results-decoration,
.vs__search::-ms-clear {
  display: none;
}

For some reason, chrome would ignore the declaration when it is grouped.

---

Closes #886

[coveralls]

Coverage remained the same at 95.982% when pulling 941f618 on fix-chrome-search-input-css into 38f291a on master.