Bug 224807

Context: WebKit supports the `-webkit-inline-flex`/`-webkit-flex` values for the CSS `display` property. They are aliases for `inline-flex`/`flex` specifically. Right now, those values are handled as separate `DisplayType` (see https://webkit-search.igalia.com/webkit/rev/240c1d5ec6ecbabd0053aad3ea5e985e53198714/Source/WebCore/rendering/style/RenderStyleConstants.h#908,910), instead we'd like to alias them directly at parse time in the `consumeDisplay` function of CSSPropertyParser.cpp. This does change the serialization (what is returned when you do `element.style.display` or `getComputedStyle(element).display`) of `-webkit-flex`/`-webkit-inline-flex` to `flex`/`inline-flex`, but this change is ok. Some tests may need to be updated to reflect this though. Steps to fix: * Add special cases directly at the beginning of the `consumeDisplay` function: ``` // Convert -webkit-flex/-webkit-inline-flex to flex/inline-flex if (range.peek().id() == CSSValueWebkitInlineFlex) return consumeIdent(range); if (range.peek().id() == CSSValueWebkitFlex) return consumeIdent(range); ``` * Move -webkit-flex/-webkit-inline-flex in Source/WebCore/css/CSSValueKeywords.in after `flow`, to avoid breaking `DisplayType display = static_cast<DisplayType>(m_value.valueID - CSSValueInline);` in CSSPrimitiveValue.cpp * Remove the WebKitFlex/WebKitInlineFlex values from the `DisplayType` enum. * Also remove all their usages too: https://webkit-search.igalia.com/webkit/search?q=DisplayType%3A%3AWebKitFlex&path=&case=false&regexp=false https://webkit-search.igalia.com/webkit/search?q=DisplayType%3A%3AWebKitInlineFlex&path=&case=false&regexp=false * Fix all potential failing tests (You'll find those by running `Tools/Scripts/run-webkit-tests --no-retry --no-show LayoutTests/` or by submitting the patch on Bugzilla and checking EWS failures). The failures will be due tests expecting `-webkit-flex`/`-webkit-inline-flex` instead of the unprefixed version when serializing. The tests should be changed to reflect that. Please feel free to reach out on the WebKit Slack for any questions (I'm @ntim).