Bug 824592 part 2. Give nsStyledElement an IID. r=peterv

dom/base/nsStyledElement.cpp

@@ -25,6 +25,10 @@
 using namespace mozilla;
 using namespace mozilla::dom;
 
+NS_IMPL_QUERY_INTERFACE_INHERITED(nsStyledElement,
+                                  nsStyledElementBase,
+                                  nsStyledElement)
+
 //----------------------------------------------------------------------
 // nsIContent methods
 

dom/base/nsStyledElement.h

@@ -23,6 +23,11 @@ class Declaration;
 } // namespace css
 } // namespace mozilla
 
+// IID for nsStyledElement interface
+#define NS_STYLED_ELEMENT_IID \
+{ 0xacbd9ea6, 0x15aa, 0x4f37, \
+ { 0x8c, 0xe0, 0x35, 0x1e, 0xd7, 0x21, 0xca, 0xe9 } }
+
 typedef mozilla::dom::Element nsStyledElementBase;
 
 class nsStyledElement : public nsStyledElementBase
@@ -35,6 +40,11 @@ protected:
   {}
 
 public:
+  // We don't want to implement AddRef/Release because that would add an extra
+  // function call for those on pretty much all elements.  But we do need QI, so
+  // we can QI to nsStyledElement.
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
   // Element interface methods
   virtual mozilla::css::Declaration* GetInlineStyleDeclaration() override;
   virtual nsresult SetInlineStyleDeclaration(mozilla::css::Declaration* aDeclaration,
@@ -43,6 +53,8 @@ public:
 
   nsICSSDeclaration* Style();
 
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_STYLED_ELEMENT_IID)
+
 protected:
 
   /**
@@ -70,4 +82,5 @@ protected:
   nsresult  ReparseStyleAttribute(bool aForceInDataDoc);
 };
 
+NS_DEFINE_STATIC_IID_ACCESSOR(nsStyledElement, NS_STYLED_ELEMENT_IID)
 #endif // __NS_STYLEDELEMENT_H_