--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -442,16 +442,22 @@ Servo_Initialize()
 
 void
 Servo_RestyleDocument(RawGeckoDocument* doc, RawServoStyleSet* set)
 {
   MOZ_CRASH("stylo: shouldn't be calling Servo_RestyleDocument in a "
             "non-MOZ_STYLO build");
 }
 
+void Servo_RestyleSubtree(RawGeckoNode* node, RawServoStyleSet* set)
+{
+  MOZ_CRASH("stylo: shouldn't be calling Servo_RestyleSubtree in a "
+            "non-MOZ_STYLO build");
+}
+
 #define STYLE_STRUCT(name_, checkdata_cb_)                                     \
 const nsStyle##name_*                                                          \
 Servo_GetStyle##name_(ServoComputedValues*)                                    \
 {                                                                              \
   MOZ_CRASH("stylo: shouldn't be calling Servo_GetStyle" #name_ " in a "       \
             "non-MOZ_STYLO build");                                            \
 }
 #include "nsStyleStructList.h"

--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -150,18 +150,19 @@ ServoComputedValues* Servo_GetComputedVa
                                                              bool is_probe);
 ServoComputedValues* Servo_InheritComputedValues(ServoComputedValues* parent_style);
 void Servo_AddRefComputedValues(ServoComputedValues*);
 void Servo_ReleaseComputedValues(ServoComputedValues*);
 
 // Initialize Servo components. Should be called exactly once at startup.
 void Servo_Initialize();
 
-// Restyle the given document.
+// Restyle the given document or subtree.
 void Servo_RestyleDocument(RawGeckoDocument* doc, RawServoStyleSet* set);
+void Servo_RestyleSubtree(RawGeckoNode* node, RawServoStyleSet* set);
 
 // Style-struct management.
 #define STYLE_STRUCT(name, checkdata_cb) \
 struct nsStyle##name; \
 void Gecko_Construct_nsStyle##name(nsStyle##name* ptr); \
 void Gecko_CopyConstruct_nsStyle##name(nsStyle##name* ptr, const nsStyle##name* other); \
 void Gecko_Destroy_nsStyle##name(nsStyle##name* ptr); \
 const nsStyle##name* Servo_GetStyle##name(ServoComputedValues* computedValues);

--- a/layout/style/ServoStyleSet.cpp
+++ b/layout/style/ServoStyleSet.cpp
@@ -378,8 +378,14 @@ ServoStyleSet::HasStateDependentStyle(do
 nsRestyleHint
 ServoStyleSet::HasStateDependentStyle(dom::Element* aElement,
                                       CSSPseudoElementType aPseudoType,
                                      dom::Element* aPseudoElement,
                                      EventStates aStateMask)
 {
   MOZ_CRASH("stylo: not implemented");
 }
+
+void
+ServoStyleSet::RestyleSubtree(nsINode* aNode)
+{
+  Servo_RestyleSubtree(aNode, mRawSet.get());
+}

--- a/layout/style/ServoStyleSet.h
+++ b/layout/style/ServoStyleSet.h
@@ -111,16 +111,18 @@ public:
   // Test if style is dependent on content state
   nsRestyleHint HasStateDependentStyle(dom::Element* aElement,
                                        EventStates aStateMask);
   nsRestyleHint HasStateDependentStyle(dom::Element* aElement,
                                        mozilla::CSSPseudoElementType aPseudoType,
                                        dom::Element* aPseudoElement,
                                        EventStates aStateMask);
 
+  void RestyleSubtree(nsINode* aNode);
+
 private:
   already_AddRefed<nsStyleContext> GetContext(already_AddRefed<ServoComputedValues>,
                                               nsStyleContext* aParentContext,
                                               nsIAtom* aPseudoTag,
                                               CSSPseudoElementType aPseudoType);
 
   already_AddRefed<nsStyleContext> GetContext(nsIContent* aContent,
                                               nsStyleContext* aParentContext,