patch.patch

diff --git a/layout/style/ServoBindings.cpp b/layout/style/ServoBindings.cpp
index 5e0c78a..bbb3f51 100644
--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -313,7 +313,7 @@ Gecko_StoreStyleDifference(RawGeckoNodeBorrowed aNode, nsChangeHint aChangeHintT
 #endif
 }
 
-RawServoDeclarationBlock*
+RawServoDeclarationBlockStrongBorrowedOrNull
 Gecko_GetServoDeclarationBlock(RawGeckoElementBorrowed aElement)
 {
   const nsAttrValue* attr = aElement->GetParsedAttr(nsGkAtoms::style);
@@ -324,7 +324,7 @@ Gecko_GetServoDeclarationBlock(RawGeckoElementBorrowed aElement)
   if (!decl || decl->IsGecko()) {
     return nullptr;
   }
-  return decl->AsServo()->Raw();
+  return reinterpret_cast<RawServoDeclarationBlockStrongBorrowedOrNull>(const_cast<RawServoDeclarationBlock**>(&decl->AsServo()->Raw()));
 }
 
 void
diff --git a/layout/style/ServoBindings.h b/layout/style/ServoBindings.h
index 2d4e4a6..e544a60 100644
--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -102,6 +102,7 @@ using mozilla::dom::StyleChildrenIterator;
 DECL_ARC_REF_TYPE_FOR(ServoComputedValues)
 DECL_ARC_REF_TYPE_FOR(RawServoStyleSheet)
 DECL_ARC_REF_TYPE_FOR(RawServoDeclarationBlock)
+DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawServoDeclarationBlockStrong)
 
 DECL_OWNED_REF_TYPE_FOR(RawServoStyleSet)
 DECL_NULLABLE_OWNED_REF_TYPE_FOR(StyleChildrenIterator)
@@ -216,7 +217,7 @@ SERVO_DECLARE_ELEMENT_ATTR_MATCHING_FUNCTIONS(Gecko_Snapshot,
 #undef SERVO_DECLARE_ELEMENT_ATTR_MATCHING_FUNCTIONS
 
 // Style attributes.
-RawServoDeclarationBlockBorrowedOrNull
+RawServoDeclarationBlockStrongBorrowedOrNull
 Gecko_GetServoDeclarationBlock(RawGeckoElementBorrowed element);
 
 // Atoms.
diff --git a/layout/style/ServoDeclarationBlock.h b/layout/style/ServoDeclarationBlock.h
index 16b26bd..edc02e1 100644
--- a/layout/style/ServoDeclarationBlock.h
+++ b/layout/style/ServoDeclarationBlock.h
@@ -19,7 +19,9 @@ public:
   static already_AddRefed<ServoDeclarationBlock>
   FromStyleAttribute(const nsAString& aString);
 
-  RawServoDeclarationBlock* Raw() const { return mRaw; }
+  RawServoDeclarationBlock* const& Raw() const {
+    return *reinterpret_cast<RawServoDeclarationBlock* const*>(mRaw.get_address());
+  }
 
 protected:
   ServoDeclarationBlock(already_AddRefed<RawServoDeclarationBlock> aRaw)
diff --git a/servo/components/style/binding_tools/regen.py b/servo/components/style/binding_tools/regen.py
index fc0cc24..8e775e54 100755
--- a/servo/components/style/binding_tools/regen.py
+++ b/servo/components/style/binding_tools/regen.py
@@ -242,6 +242,7 @@ COMPILATION_TARGETS = {
             "RawGeckoNode",
             "RawGeckoElement",
             "RawGeckoDocument",
+            "RawServoDeclarationBlockStrong",
         ],
         "whitelist_functions": [
             "Servo_.*",
diff --git a/servo/components/style/gecko/wrapper.rs b/servo/components/style/gecko/wrapper.rs
index 398e114..c4f5f36 100644
--- a/servo/components/style/gecko/wrapper.rs
+++ b/servo/components/style/gecko/wrapper.rs
@@ -30,7 +30,7 @@ use gecko_bindings::structs::{NODE_HAS_DIRTY_DESCENDANTS_FOR_SERVO, NODE_IS_DIRT
 use gecko_bindings::structs::{RawGeckoDocument, RawGeckoElement, RawGeckoNode};
 use gecko_bindings::structs::{nsChangeHint, nsIAtom, nsIContent, nsStyleContext};
 use gecko_bindings::structs::OpaqueStyleData;
-use gecko_bindings::sugar::ownership::{FFIArcHelpers, HasArcFFI};
+use gecko_bindings::sugar::ownership::FFIArcHelpers;
 use libc::uintptr_t;
 use parking_lot::RwLock;
 use parser::ParserContextExtraData;
@@ -482,8 +482,7 @@ impl<'le> TElement for GeckoElement<'le> {
 
     fn style_attribute(&self) -> Option<&Arc<RwLock<PropertyDeclarationBlock>>> {
         let declarations = unsafe { Gecko_GetServoDeclarationBlock(self.0) };
-        RwLock::<PropertyDeclarationBlock>::arc_from_borrowed(&declarations)
-            .map(|decl| decl as *const Arc<_>).map(|ptr| unsafe { &*ptr })
+        declarations.map(|s| s.into_arc_opt_borrow()).unwrap_or(None)
     }
 
     fn get_state(&self) -> ElementState {
diff --git a/servo/components/style/gecko_bindings/bindings.rs b/servo/components/style/gecko_bindings/bindings.rs
index 1a05e81..3df0348 100644
--- a/servo/components/style/gecko_bindings/bindings.rs
+++ b/servo/components/style/gecko_bindings/bindings.rs
@@ -21,6 +21,8 @@ pub type RawGeckoElementBorrowed<'a> = &'a RawGeckoElement;
 pub type RawGeckoElementBorrowedOrNull<'a> = Option<&'a RawGeckoElement>;
 pub type RawGeckoDocumentBorrowed<'a> = &'a RawGeckoDocument;
 pub type RawGeckoDocumentBorrowedOrNull<'a> = Option<&'a RawGeckoDocument>;
+pub type RawServoDeclarationBlockStrongBorrowed<'a> = &'a RawServoDeclarationBlockStrong;
+pub type RawServoDeclarationBlockStrongBorrowedOrNull<'a> = Option<&'a RawServoDeclarationBlockStrong>;
 pub type RawServoStyleSetBorrowed<'a> = &'a RawServoStyleSet;
 pub type RawServoStyleSetBorrowedMut<'a> = &'a mut RawServoStyleSet;
 pub type RawServoStyleSetOwned = ::gecko_bindings::sugar::ownership::Owned<RawServoStyleSet>;
@@ -359,7 +361,7 @@ extern "C" {
 }
 extern "C" {
     pub fn Gecko_GetServoDeclarationBlock(element: RawGeckoElementBorrowed)
-     -> RawServoDeclarationBlockBorrowedOrNull;
+     -> RawServoDeclarationBlockStrongBorrowedOrNull;
 }
 extern "C" {
     pub fn Gecko_Atomize(aString: *const ::std::os::raw::c_char, aLength: u32)
diff --git a/servo/components/style/gecko_bindings/sugar/ownership.rs b/servo/components/style/gecko_bindings/sugar/ownership.rs
index bd31483..de29c2d 100644
--- a/servo/components/style/gecko_bindings/sugar/ownership.rs
+++ b/servo/components/style/gecko_bindings/sugar/ownership.rs
@@ -162,6 +162,20 @@ impl<T> Strong<T> {
     }
 
     #[inline]
+    /// Given a reference to a strong FFI reference,
+    /// converts it into a reference to a servo-side Arc
+    /// Returns None on null.
+    ///
+    /// Strong<GeckoType> -> Arc<ServoType>
+    pub fn into_arc_opt_borrow<U>(&self) -> Option<&Arc<U>> where U: HasArcFFI<FFIType = T> {
+        if self.is_null() {
+            None
+        } else {
+            unsafe { Some(transmute(self)) }
+        }
+    }
+
+    #[inline]
     /// Produces a null strong FFI reference
     pub fn null() -> Self {
         unsafe { transmute(ptr::null::<T>()) }