Auto merge of #17974 - froydnj:remove-testing-feature, r=SimonSapin

remove testing feature from stylo_tests

`stylo_tests` currently requires a separate version of the `style` crate, compiled with the `testing` feature, so a function testing the size of specified values can be accessed.  With a few tweaks, we can make the information needed for the test available to the `stylo_tests` crate directly, eliminating the need for a separately-compiled `style` crate.

This doesn't matter much for Servo itself (it might make CI times slightly faster?), but Gecko automation/development would like to run `stylo_tests`, and not having to compile two versions of the `style` crate (or have a dead, test-only function hanging around in the `style` crate) would be a win.

---

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] There are tests for these changes

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components/style/lib.rs

@@ -171,7 +171,7 @@ pub mod gecko_properties {
 }
 
 macro_rules! reexport_computed_values {
-    ( $( $name: ident )+ ) => {
+    ( $( { $name: ident, $boxed: expr } )+ ) => {
         /// Types for [computed values][computed].
         ///
         /// [computed]: https://drafts.csswg.org/css-cascade/#computed

components/style/properties/properties.mako.rs

@@ -3442,49 +3442,13 @@ macro_rules! css_properties_accessors {
     }
 }
 
-
+#[macro_export]
 macro_rules! longhand_properties_idents {
     ($macro_name: ident) => {
         $macro_name! {
             % for property in data.longhands:
-                ${property.ident}
+                { ${property.ident}, ${"true" if property.boxed else "false"} }
             % endfor
         }
     }
 }
-
-/// Testing function to check the size of all SpecifiedValues.
-#[cfg(feature = "testing")]
-pub fn test_size_of_specified_values() {
-    use std::mem::size_of;
-    let threshold = 24;
-
-    let mut longhands = vec![];
-    % for property in data.longhands:
-        longhands.push(("${property.name}",
-                       size_of::<longhands::${property.ident}::SpecifiedValue>(),
-                       ${"true" if property.boxed else "false"}));
-    % endfor
-
-    let mut failing_messages = vec![];
-
-    for specified_value in longhands {
-        if specified_value.1 > threshold && !specified_value.2 {
-            failing_messages.push(
-                format!("Your changes have increased the size of {} SpecifiedValue to {}. The threshold is \
-                        currently {}. SpecifiedValues affect size of PropertyDeclaration enum and \
-                        increasing the size may negative affect style system performance. Please consider \
-                        using `boxed=\"True\"` in this longhand.",
-                        specified_value.0, specified_value.1, threshold));
-        } else if specified_value.1 <= threshold && specified_value.2 {
-            failing_messages.push(
-                format!("Your changes have decreased the size of {} SpecifiedValue to {}. Good work! \
-                        The threshold is currently {}. Please consider removing `boxed=\"True\"` from this longhand.",
-                        specified_value.0, specified_value.1, threshold));
-        }
-    }
-
-    if !failing_messages.is_empty() {
-        panic!("{}", failing_messages.join("\n\n"));
-    }
-}