Auto merge of #18310 - nnethercote:bug-1394729, r=heycam

Measure memory usage of Stylo's Rule Tree.

<!-- Please describe your changes on the following line: -->
This is for https://bugzilla.mozilla.org/show_bug.cgi?id=1394729, which was r=heycam.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [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
- [X] These changes do not require tests because tests exist in Gecko.

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components/style/gecko/data.rs

@@ -7,8 +7,8 @@
 use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
 use dom::TElement;
 use gecko_bindings::bindings::{self, RawServoStyleSet};
-use gecko_bindings::structs::{ServoStyleSheet, StyleSheetInfo, ServoStyleSheetInner};
-use gecko_bindings::structs::RawGeckoPresContextOwned;
+use gecko_bindings::structs::{RawGeckoPresContextOwned, ServoStyleSetSizes, ServoStyleSheet};
+use gecko_bindings::structs::{StyleSheetInfo, ServoStyleSheetInner};
 use gecko_bindings::structs::nsIDocument;
 use gecko_bindings::sugar::ownership::{HasArcFFI, HasBoxFFI, HasFFI, HasSimpleFFI};
 use invalidation::media_queries::{MediaListKey, ToMediaListKey};
@@ -16,7 +16,7 @@ use media_queries::{Device, MediaList};
 use properties::ComputedValues;
 use servo_arc::Arc;
 use shared_lock::{Locked, StylesheetGuards, SharedRwLockReadGuard};
-use stylesheets::{PerOrigin, StylesheetContents, StylesheetInDocument};
+use stylesheets::{MallocSizeOfFn, PerOrigin, StylesheetContents, StylesheetInDocument};
 use stylist::{ExtraStyleData, Stylist};
 
 /// Little wrapper to a Gecko style sheet.
@@ -184,6 +184,14 @@ impl PerDocumentStyleDataImpl {
     pub fn visited_styles_enabled(&self) -> bool {
         self.visited_links_enabled() && !self.is_private_browsing_enabled()
     }
+
+    /// Measures heap usage.
+    pub fn malloc_add_size_of_children(&self, malloc_size_of: MallocSizeOfFn,
+                                       sizes: &mut ServoStyleSetSizes) {
+        self.stylist.malloc_add_size_of_children(malloc_size_of, sizes);
+
+        // We may measure more fields in the future if DMD says it's worth it.
+    }
 }
 
 unsafe impl HasFFI for PerDocumentStyleData {

components/style/gecko/generated/bindings.rs

@@ -61,6 +61,7 @@ use gecko_bindings::structs::SeenPtrs;
 use gecko_bindings::structs::ServoBundledURI;
 use gecko_bindings::structs::ServoElementSnapshot;
 use gecko_bindings::structs::ServoElementSnapshotTable;
+use gecko_bindings::structs::ServoStyleSetSizes;
 use gecko_bindings::structs::SheetParsingMode;
 use gecko_bindings::structs::StyleBasicShape;
 use gecko_bindings::structs::StyleBasicShapeType;
@@ -2067,6 +2068,11 @@ extern "C" {
                                                      RawServoDeclarationBlockBorrowed)
      -> ServoStyleContextStrong;
 }
+extern "C" {
+    pub fn Servo_StyleSet_AddSizeOfExcludingThis(malloc_size_of: MallocSizeOf,
+                                                 sizes: *mut ServoStyleSetSizes,
+                                                 set: RawServoStyleSetBorrowed);
+}
 extern "C" {
     pub fn Servo_StyleContext_AddRef(ctx: ServoStyleContextBorrowed);
 }

components/style/gecko/generated/structs_debug.rs

@@ -5456,6 +5456,38 @@ pub mod root {
                         "Alignment of field: " , stringify ! ( GeckoEffects )
                         , "::" , stringify ! ( gecko ) ));
         }
+        #[repr(C)]
+        #[derive(Debug, Copy)]
+        pub struct ServoStyleSetSizes {
+            pub mStylistRuleTree: usize,
+            pub mOther: usize,
+        }
+        #[test]
+        fn bindgen_test_layout_ServoStyleSetSizes() {
+            assert_eq!(::std::mem::size_of::<ServoStyleSetSizes>() , 16usize ,
+                       concat ! (
+                       "Size of: " , stringify ! ( ServoStyleSetSizes ) ));
+            assert_eq! (::std::mem::align_of::<ServoStyleSetSizes>() , 8usize
+                        , concat ! (
+                        "Alignment of " , stringify ! ( ServoStyleSetSizes )
+                        ));
+            assert_eq! (unsafe {
+                        & ( * ( 0 as * const ServoStyleSetSizes ) ) .
+                        mStylistRuleTree as * const _ as usize } , 0usize ,
+                        concat ! (
+                        "Alignment of field: " , stringify ! (
+                        ServoStyleSetSizes ) , "::" , stringify ! (
+                        mStylistRuleTree ) ));
+            assert_eq! (unsafe {
+                        & ( * ( 0 as * const ServoStyleSetSizes ) ) . mOther
+                        as * const _ as usize } , 8usize , concat ! (
+                        "Alignment of field: " , stringify ! (
+                        ServoStyleSetSizes ) , "::" , stringify ! ( mOther )
+                        ));
+        }
+        impl Clone for ServoStyleSetSizes {
+            fn clone(&self) -> Self { *self }
+        }
         #[repr(u8)]
         /// Enumeration that represents one of the two supported style system backends.
         #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]

components/style/gecko/generated/structs_release.rs

@@ -5344,6 +5344,38 @@ pub mod root {
                         "Alignment of field: " , stringify ! ( GeckoEffects )
                         , "::" , stringify ! ( gecko ) ));
         }
+        #[repr(C)]
+        #[derive(Debug, Copy)]
+        pub struct ServoStyleSetSizes {
+            pub mStylistRuleTree: usize,
+            pub mOther: usize,
+        }
+        #[test]
+        fn bindgen_test_layout_ServoStyleSetSizes() {
+            assert_eq!(::std::mem::size_of::<ServoStyleSetSizes>() , 16usize ,
+                       concat ! (
+                       "Size of: " , stringify ! ( ServoStyleSetSizes ) ));
+            assert_eq! (::std::mem::align_of::<ServoStyleSetSizes>() , 8usize
+                        , concat ! (
+                        "Alignment of " , stringify ! ( ServoStyleSetSizes )
+                        ));
+            assert_eq! (unsafe {
+                        & ( * ( 0 as * const ServoStyleSetSizes ) ) .
+                        mStylistRuleTree as * const _ as usize } , 0usize ,
+                        concat ! (
+                        "Alignment of field: " , stringify ! (
+                        ServoStyleSetSizes ) , "::" , stringify ! (
+                        mStylistRuleTree ) ));
+            assert_eq! (unsafe {
+                        & ( * ( 0 as * const ServoStyleSetSizes ) ) . mOther
+                        as * const _ as usize } , 8usize , concat ! (
+                        "Alignment of field: " , stringify ! (
+                        ServoStyleSetSizes ) , "::" , stringify ! ( mOther )
+                        ));
+        }
+        impl Clone for ServoStyleSetSizes {
+            fn clone(&self) -> Self { *self }
+        }
         #[repr(u8)]
         /// Enumeration that represents one of the two supported style system backends.
         #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]