Bug 1317209 - Part 3: Add constness to GetEffectSet. r=hiro

We need to call GetEffectSet() from Servo code, which passes an
immutable reference to GeckoElement, so it's better to make dom::Element
const.

MozReview-Commit-ID: GqQEB7BwkJA

--HG--
extra : rebase_source : 4b025f56949d8327781be26d1607e6d9f4668f2f

dom/animation/EffectSet.cpp

@@ -39,7 +39,7 @@ EffectSet::Traverse(nsCycleCollectionTraversalCallback& aCallback)
 }
 
 /* static */ EffectSet*
-EffectSet::GetEffectSet(dom::Element* aElement,
+EffectSet::GetEffectSet(const dom::Element* aElement,
                         CSSPseudoElementType aPseudoType)
 {
   nsIAtom* propName = GetEffectSetPropertyAtom(aPseudoType);

dom/animation/EffectSet.h

@@ -57,7 +57,7 @@ public:
   // Methods for supporting cycle-collection
   void Traverse(nsCycleCollectionTraversalCallback& aCallback);
 
-  static EffectSet* GetEffectSet(dom::Element* aElement,
+  static EffectSet* GetEffectSet(const dom::Element* aElement,
                                  CSSPseudoElementType aPseudoType);
   static EffectSet* GetEffectSet(const nsIFrame* aFrame);
   static EffectSet* GetOrCreateEffectSet(dom::Element* aElement,