--- a/layout/base/GeckoRestyleManager.cpp
+++ b/layout/base/GeckoRestyleManager.cpp
@@ -195,34 +195,33 @@ GeckoRestyleManager::ReframingStyleConte
 
 static inline dom::Element*
 ElementForStyleContext(nsIContent* aParentContent,
                        nsIFrame* aFrame,
                        CSSPseudoElementType aPseudoType);
 
 // Forwarded nsIDocumentObserver method, to handle restyling (and
 // passing the notification to the frame).
-nsresult
+void
 GeckoRestyleManager::ContentStateChanged(nsIContent* aContent,
                                          EventStates aStateMask)
 {
   // XXXbz it would be good if this function only took Elements, but
   // we'd have to make ESM guarantee that usefully.
   if (!aContent->IsElement()) {
-    return NS_OK;
+    return;
   }
 
   Element* aElement = aContent->AsElement();
 
   nsChangeHint changeHint;
   nsRestyleHint restyleHint;
   ContentStateChangedInternal(aElement, aStateMask, &changeHint, &restyleHint);
 
   PostRestyleEvent(aElement, restyleHint, changeHint);
-  return NS_OK;
 }
 
 // Forwarded nsIMutationObserver method, to handle restyling.
 void
 GeckoRestyleManager::AttributeWillChange(Element* aElement,
                                          int32_t aNameSpaceID,
                                          nsIAtom* aAttribute,
                                          int32_t aModType,

--- a/layout/base/GeckoRestyleManager.h
+++ b/layout/base/GeckoRestyleManager.h
@@ -49,18 +49,18 @@ protected:
   {
     MOZ_ASSERT(!mReframingStyleContexts,
                "temporary member should be nulled out before destruction");
   }
 
 public:
   // Forwarded nsIDocumentObserver method, to handle restyling (and
   // passing the notification to the frame).
-  nsresult ContentStateChanged(nsIContent*   aContent,
-                               EventStates aStateMask);
+  void ContentStateChanged(nsIContent* aContent,
+                           EventStates aStateMask);
 
   // Forwarded nsIMutationObserver method, to handle restyling.
   void AttributeWillChange(Element* aElement,
                            int32_t  aNameSpaceID,
                            nsIAtom* aAttribute,
                            int32_t  aModType,
                            const nsAttrValue* aNewValue);
   // Forwarded nsIMutationObserver method, to handle restyling (and

--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -169,18 +169,18 @@ public:
   inline void PostRestyleEvent(dom::Element* aElement,
                                nsRestyleHint aRestyleHint,
                                nsChangeHint aMinChangeHint);
   inline void RebuildAllStyleData(nsChangeHint aExtraHint,
                                   nsRestyleHint aRestyleHint);
   inline void PostRebuildAllStyleDataEvent(nsChangeHint aExtraHint,
                                            nsRestyleHint aRestyleHint);
   inline void ProcessPendingRestyles();
-  inline nsresult ContentStateChanged(nsIContent* aContent,
-                                      EventStates aStateMask);
+  inline void ContentStateChanged(nsIContent* aContent,
+                                  EventStates aStateMask);
   inline void AttributeWillChange(dom::Element* aElement,
                                   int32_t aNameSpaceID,
                                   nsIAtom* aAttribute,
                                   int32_t aModType,
                                   const nsAttrValue* aNewValue);
   inline void AttributeChanged(dom::Element* aElement,
                                int32_t aNameSpaceID,
                                nsIAtom* aAttribute,

--- a/layout/base/RestyleManagerInlines.h
+++ b/layout/base/RestyleManagerInlines.h
@@ -39,17 +39,17 @@ RestyleManager::PostRebuildAllStyleDataE
 }
 
 void
 RestyleManager::ProcessPendingRestyles()
 {
   MOZ_STYLO_FORWARD(ProcessPendingRestyles, ());
 }
 
-nsresult
+void
 RestyleManager::ContentStateChanged(nsIContent* aContent,
                                     EventStates aStateMask)
 {
   MOZ_STYLO_FORWARD(ContentStateChanged, (aContent, aStateMask));
 }
 
 void
 RestyleManager::AttributeWillChange(dom::Element* aElement,

--- a/layout/base/ServoRestyleManager.cpp
+++ b/layout/base/ServoRestyleManager.cpp
@@ -464,22 +464,22 @@ ServoRestyleManager::RestyleForAppend(ns
 void
 ServoRestyleManager::ContentRemoved(nsINode* aContainer,
                                     nsIContent* aOldChild,
                                     nsIContent* aFollowingSibling)
 {
   NS_WARNING("stylo: ServoRestyleManager::ContentRemoved not implemented");
 }
 
-nsresult
+void
 ServoRestyleManager::ContentStateChanged(nsIContent* aContent,
                                          EventStates aChangedBits)
 {
   if (!aContent->IsElement()) {
-    return NS_OK;
+    return;
   }
 
   Element* aElement = aContent->AsElement();
   nsChangeHint changeHint;
   nsRestyleHint restyleHint;
 
   // NOTE: restyleHint here is effectively always 0, since that's what
   // ServoStyleSet::HasStateDependentStyle returns. Servo computes on
@@ -504,18 +504,16 @@ ServoRestyleManager::ContentStateChanged
                               &restyleHint);
 
   EventStates previousState = aElement->StyleState() ^ aChangedBits;
   ServoElementSnapshot* snapshot = Servo_Element_GetSnapshot(aElement);
   if (snapshot) {
     snapshot->AddState(previousState);
     PostRestyleEvent(aElement, restyleHint, changeHint);
   }
-
-  return NS_OK;
 }
 
 void
 ServoRestyleManager::AttributeWillChange(Element* aElement,
                                          int32_t aNameSpaceID,
                                          nsIAtom* aAttribute, int32_t aModType,
                                          const nsAttrValue* aNewValue)
 {

--- a/layout/base/ServoRestyleManager.h
+++ b/layout/base/ServoRestyleManager.h
@@ -58,18 +58,17 @@ public:
   void ContentRemoved(nsINode* aContainer,
                       nsIContent* aOldChild,
                       nsIContent* aFollowingSibling);
 
   void RestyleForInsertOrChange(nsINode* aContainer,
                                 nsIContent* aChild);
   void RestyleForAppend(nsIContent* aContainer,
                         nsIContent* aFirstNewContent);
-  nsresult ContentStateChanged(nsIContent* aContent,
-                               EventStates aStateMask);
+  void ContentStateChanged(nsIContent* aContent, EventStates aStateMask);
   void AttributeWillChange(dom::Element* aElement,
                            int32_t aNameSpaceID,
                            nsIAtom* aAttribute,
                            int32_t aModType,
                            const nsAttrValue* aNewValue);
 
   void AttributeChanged(dom::Element* aElement, int32_t aNameSpaceID,
                         nsIAtom* aAttribute, int32_t aModType,