style: Don't apply property restrictions to pseudo-elements in UA sty…

…lesheets.

And remove some of the ::placeholder and ::cue hacks where we need to use
!important to make the property not apply for content but apply on UA sheets.

The comment about the white-space property was wrong, we don't enforce it with
!important in the UA stylesheets for <input> (we do for <textarea> though), so
I've kept the flag since it really applies.

Differential Revision: https://phabricator.services.mozilla.com/D37717

components/style/properties/cascade.rs

@@ -153,7 +153,7 @@ where
                         // longhands are only allowed if they have our
                         // restriction flag set.
                         if let PropertyDeclarationId::Longhand(id) = declaration.id() {
-                            if !id.flags().contains(restriction) {
+                            if !id.flags().contains(restriction) && cascade_level.origin() != Origin::UserAgent {
                                 return None;
                             }
                         }

components/style/properties/longhands/box.mako.rs

@@ -9,15 +9,12 @@
                          inherited=False,
                          gecko_name="Display") %>
 
-// We allow "display" to apply to placeholders because we need to make the
-// placeholder pseudo-element an inline-block in the UA stylesheet in Gecko.
 ${helpers.predefined_type(
     "display",
     "Display",
     "computed::Display::inline()",
     initial_specified_value="specified::Display::inline()",
     animation_value_type="discrete",
-    flags="APPLIES_TO_PLACEHOLDER",
     spec="https://drafts.csswg.org/css-display/#propdef-display",
     servo_restyle_damage="rebuild_and_reflow",
     needs_context=product == "gecko"
@@ -103,17 +100,13 @@ ${helpers.single_keyword("-servo-overflow-clip-box", "padding-box content-box",
         products="gecko",
         enabled_in="ua",
         needs_context=False,
-        flags="APPLIES_TO_PLACEHOLDER",
         gecko_pref="layout.css.overflow-clip-box.enabled",
         animation_value_type="discrete",
         spec="Internal, may be standardized in the future: \
               https://developer.mozilla.org/en-US/docs/Web/CSS/overflow-clip-box",
     )}
 % endfor
 
-// FIXME(pcwalton, #2742): Implement scrolling for `scroll` and `auto`.
-//
-// We allow it to apply to placeholders for UA sheets, which set it !important.
 % for (axis, logical) in ALL_AXES:
     <% full_name = "overflow-{}".format(axis) %>
     ${helpers.predefined_type(
@@ -123,7 +116,6 @@ ${helpers.single_keyword("-servo-overflow-clip-box", "padding-box content-box",
         logical_group="overflow",
         logical=logical,
         animation_value_type="discrete",
-        flags="APPLIES_TO_PLACEHOLDER",
         spec="https://drafts.csswg.org/css-overflow-3/#propdef-{}".format(full_name),
         needs_context=False,
         servo_restyle_damage = "reflow",
@@ -477,10 +469,6 @@ ${helpers.predefined_type(
 
 // CSS Basic User Interface Module Level 3
 // http://dev.w3.org/csswg/css-ui
-//
-// This is APPLIES_TO_PLACEHOLDER so we can override, in the UA sheet, the
-// 'resize' property we'd inherit from textarea otherwise.  Basically, just
-// makes the UA rules easier to write.
 ${helpers.predefined_type(
     "resize",
     "Resize",
@@ -489,7 +477,6 @@ ${helpers.predefined_type(
     animation_value_type="discrete",
     needs_context=False,
     gecko_ffi_name="mResize",
-    flags="APPLIES_TO_PLACEHOLDER",
     spec="https://drafts.csswg.org/css-ui/#propdef-resize",
 )}
 

components/style/properties/longhands/inherited_box.mako.rs

@@ -29,7 +29,6 @@ ${helpers.single_keyword(
     servo_pref="layout.writing-mode.enabled",
     animation_value_type="none",
     spec="https://drafts.csswg.org/css-writing-modes/#propdef-writing-mode",
-    flags="APPLIES_TO_CUE",
     servo_restyle_damage="rebuild_and_reflow",
 )}
 

components/style/properties/longhands/inherited_text.mako.rs

@@ -78,7 +78,6 @@ ${helpers.predefined_type(
     "computed::OverflowWrap::Normal",
     animation_value_type="discrete",
     spec="https://drafts.csswg.org/css-text/#propdef-overflow-wrap",
-    flags="APPLIES_TO_CUE",
     alias="word-wrap",
     needs_context=False,
     servo_restyle_damage="rebuild_and_reflow",
@@ -182,7 +181,6 @@ ${helpers.predefined_type(
     gecko_enum_prefix="StyleWhiteSpace"
     needs_conversion="True"
     animation_value_type="discrete"
-    // Only allowed for UA sheets, which set it !important.
     flags="APPLIES_TO_CUE APPLIES_TO_PLACEHOLDER"
     spec="https://drafts.csswg.org/css-text/#propdef-white-space"
     servo_restyle_damage="rebuild_and_reflow"

components/style/properties/longhands/inherited_ui.mako.rs

@@ -23,7 +23,6 @@ ${helpers.single_keyword(
     "auto none",
     animation_value_type="discrete",
     extra_gecko_values="visiblepainted visiblefill visiblestroke visible painted fill stroke all",
-    flags="APPLIES_TO_PLACEHOLDER",
     spec="https://www.w3.org/TR/SVG11/interact.html#PointerEventsProperty",
 )}
 

components/style/properties/longhands/padding.mako.rs

@@ -6,8 +6,6 @@
 <% from data import ALL_SIDES, maybe_moz_logical_alias %>
 <% data.new_style_struct("Padding", inherited=False) %>
 
-// APPLIES_TO_PLACEHOLDER so we can set it in UA  stylesheets.  But we use a
-// !important value there, so pages can't set it.
 % for side in ALL_SIDES:
     <%
         spec = "https://drafts.csswg.org/css-box/#propdef-padding-%s" % side[0]
@@ -23,7 +21,7 @@
         logical=side[1],
         logical_group="padding",
         spec=spec,
-        flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_PLACEHOLDER GETCS_NEEDS_LAYOUT_FLUSH",
+        flags="APPLIES_TO_FIRST_LETTER GETCS_NEEDS_LAYOUT_FLUSH",
         allow_quirks="No" if side[1] else "Yes",
         servo_restyle_damage="reflow rebuild_and_reflow_inline"
     )}