Auto merge of #15953 - bholley:size_of_stylo, r=<try>

Make size_of tests measure stylo

Right now they don't, which means that we have four properties making PropertyDeclaration 16 bytes bigger than it should be.

I'm not sure if there's a better way to get these tests to run against stylo than to hoist them into the properties file, but I couldn't figure it out. This seems good enough.

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components/style/properties/longhand/inherited_svg.mako.rs

@@ -119,16 +119,19 @@ ${helpers.single_keyword("clip-rule", "nonzero evenodd",
 
 ${helpers.predefined_type("marker-start", "UrlOrNone", "Either::Second(None_)",
                           products="gecko",
+                          boxed="True",
                           animatable="False",
                           spec="https://www.w3.org/TR/SVG2/painting.html#VertexMarkerProperties")}
 
 ${helpers.predefined_type("marker-mid", "UrlOrNone", "Either::Second(None_)",
                           products="gecko",
+                          boxed="True",
                           animatable="False",
                           spec="https://www.w3.org/TR/SVG2/painting.html#VertexMarkerProperties")}
 
 ${helpers.predefined_type("marker-end", "UrlOrNone", "Either::Second(None_)",
                           products="gecko",
+                          boxed="True",
                           animatable="False",
                           spec="https://www.w3.org/TR/SVG2/painting.html#VertexMarkerProperties")}
 

components/style/properties/longhand/list.mako.rs

@@ -38,6 +38,7 @@ ${helpers.single_keyword("list-style-type", """
     spec="https://drafts.csswg.org/css-lists/#propdef-list-style-type")}
 
 ${helpers.predefined_type("list-style-image", "UrlOrNone", "Either::Second(None_)",
+                          boxed = product == "gecko",
                           initial_specified_value="Either::Second(None_)", animatable=False,
                           spec="https://drafts.csswg.org/css-lists/#propdef-list-style-image")}
 

components/style/properties/properties.mako.rs

@@ -2388,7 +2388,6 @@ macro_rules! longhand_properties_idents {
 }
 
 /// Retuns all longhands SpecifiedValue sizes. This is used in unit tests.
-#[cfg(feature = "testing")]
 pub fn specified_value_sizes() -> Vec<(&'static str, usize, bool)> {
     use std::mem::size_of;
     let mut sizes = vec![];
@@ -2401,3 +2400,51 @@ pub fn specified_value_sizes() -> Vec<(&'static str, usize, bool)> {
 
     sizes
 }
+
+#[test]
+fn size_of_property_declaration() {
+    use std::mem::size_of;
+
+    let old = 48;
+    let new = size_of::<PropertyDeclaration>();
+    if new < old {
+        panic!("Your changes have decreased the stack size of PropertyDeclaration enum from {} to {}. \
+                Good work! Please update the size in tests/unit/style/size_of.rs.",
+                old, new)
+    } else if new > old {
+        panic!("Your changes have increased the stack size of PropertyDeclaration enum from {} to {}. \
+                These enum is present in large quantities in the style, and increasing the size \
+                may negatively affect style system performance. Please consider using `boxed=\"True\"` in \
+                the longhand If you feel that the increase is necessary, update to the new size in \
+                tests/unit/style/size_of.rs.",
+                old, new)
+    }
+}
+
+#[test]
+fn size_of_specified_values() {
+    let threshold = 32;
+    let longhands = specified_value_sizes();
+
+    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"));
+    }
+}

tests/unit/style/lib.rs

@@ -30,7 +30,6 @@ mod owning_handle;
 mod parsing;
 mod properties;
 mod rule_tree;
-mod size_of;
 mod str;
 mod stylesheets;
 mod stylist;