Remove support for -webkit-line-clamp

LayoutTests/fast/css/getComputedStyle/resources/property-names.js

 // We only test properties that are exposed in all ports.
 var propertiesToTest = {
     "-webkit-animation-delay": true,
     "-webkit-animation-direction": true,
     "-webkit-animation-duration": true,
     "-webkit-animation-fill-mode": true,
     "-webkit-animation-iteration-count": true,
     "-webkit-animation-name": true,
     "-webkit-animation-play-state": true,
     "-webkit-animation-timing-function": true,
@@ skipping 33 matching lines @@
     "-webkit-font-kerning": true,
     "-webkit-font-smoothing": true,
     "-webkit-font-variant-ligatures": true,
     "-webkit-grid-column": true,
     "-webkit-grid-row": true,
     "-webkit-highlight": true,
     "-webkit-hyphenate-character": true,
     "-webkit-line-align": true,
     "-webkit-line-box-contain": true,
     "-webkit-line-break": true,
-    "-webkit-line-clamp": true,
     "-webkit-line-grid": true,
     "-webkit-line-snap": true,
     "-webkit-locale": true,
     "-webkit-margin-after-collapse": true,
     "-webkit-margin-before-collapse": true,
     "-webkit-marquee-direction": true,
     "-webkit-marquee-increment": true,
     "-webkit-marquee-repetition": true,
     "-webkit-marquee-style": true,
     "-webkit-mask-attachment": true,
@@ skipping 186 matching lines @@
 // There properties don't show up when iterating a computed style object,
 // but we do want to dump their values in tests.
 var hiddenComputedStyleProperties = [
     "background-position-x",
     "background-position-y",
     "border-spacing",
     "overflow",
     "-webkit-mask-position-x",
     "-webkit-mask-position-y",
 ];