Auto merge of #14535 - servo:property-id, r=mbrubeck

Introduce a PropertyId enum and use it instead of strings of property names

<!-- Please describe your changes on the following line: -->

* `LonghandId` and `ShorthandId` are C-like enums
* `Atom` is used for the name of custom properties.
* `PropertyDeclarationId` is the identifier for `PropertyDeclaration`,
  after parsing and shorthand expansion. (Longhand or custom property.)
* `PropertyId` represents any CSS property, e.g. in CSSOM.
  (Longhand, shorthand, or custom.)

CC @upsuper

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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2 files changed, 3 insertions, 3 deletions

diff --git a/components/script_layout_interface/message.rs b/components/script_layout_interface/message.rs
index 581adbb45bc..3d0e00c46cc 100644
--- a/components/script_layout_interface/message.rs
+++ b/components/script_layout_interface/message.rs
@@ -14,11 +14,11 @@ use profile_traits::mem::ReportsChan;
 use rpc::LayoutRPC;
 use script_traits::{ConstellationControlMsg, LayoutControlMsg};
 use script_traits::{LayoutMsg as ConstellationMsg, StackingContextScrollState, WindowSizeData};
-use servo_atoms::Atom;
 use servo_url::ServoUrl;
 use std::sync::Arc;
 use std::sync::mpsc::{Receiver, Sender};
 use style::context::ReflowGoal;
+use style::properties::PropertyId;
 use style::selector_parser::PseudoElement;
 use style::stylesheets::Stylesheet;
 
@@ -97,7 +97,7 @@ pub enum ReflowQueryType {
     NodeScrollRootIdQuery(TrustedNodeAddress),
     NodeGeometryQuery(TrustedNodeAddress),
     NodeScrollGeometryQuery(TrustedNodeAddress),
-    ResolvedStyleQuery(TrustedNodeAddress, Option<PseudoElement>, Atom),
+    ResolvedStyleQuery(TrustedNodeAddress, Option<PseudoElement>, PropertyId),
     OffsetParentQuery(TrustedNodeAddress),
     MarginStyleQuery(TrustedNodeAddress),
 }
diff --git a/components/script_layout_interface/rpc.rs b/components/script_layout_interface/rpc.rs
index 6e19b3f3bcf..7bc58dbf334 100644
--- a/components/script_layout_interface/rpc.rs
+++ b/components/script_layout_interface/rpc.rs
@@ -57,7 +57,7 @@ pub struct HitTestResponse {
     pub node_address: Option<UntrustedNodeAddress>,
 }
 
-pub struct ResolvedStyleResponse(pub Option<String>);
+pub struct ResolvedStyleResponse(pub String);
 
 #[derive(Clone)]
 pub struct OffsetParentResponse {