style: Add -webkit-appearance:progress-bar and make that the default …

…for <progress> for compatibility with other UAs.

Keep our old 'progressbar' as an alias for now, but unship
'progresschunk' by restricting it to UA/chrome sheets only.
Unship 'progresschunk-vertical' by removing it since it's
not used internally for anything.

Bug: 1501506
Reviewed-by: jwatt

components/style/values/specified/box.rs

@@ -1047,13 +1047,13 @@ pub enum Appearance {
     /// For HTML's <input type=number>
     NumberInput,
     /// A horizontal progress bar.
-    Progressbar,
+    #[parse(aliases = "progressbar")]
+    ProgressBar,
     /// The progress bar's progress indicator
+    #[parse(condition = "in_ua_or_chrome_sheet")]
     Progresschunk,
     /// A vertical progress bar.
     ProgressbarVertical,
-    /// A vertical progress chunk.
-    ProgresschunkVertical,
     /// A checkbox element.
     Checkbox,
     /// A radio element within a radio group.