Bug 1432944 part 7. Remove nsIDOMElement's tagName attribute. r=mccr8

MozReview-Commit-ID: 8rmd120L2BK

dom/base/Element.h

@@ -2196,11 +2196,6 @@ _elementName::Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult,   \
 
 #define NS_FORWARD_NSIDOMELEMENT_TO_GENERIC                                   \
 typedef mozilla::dom::Element Element;                                        \
-NS_IMETHOD GetTagName(nsAString& aTagName) final override                     \
-{                                                                             \
-  Element::GetTagName(aTagName);                                              \
-  return NS_OK;                                                               \
-}                                                                             \
 using Element::GetAttribute;                                                  \
 NS_IMETHOD GetAttribute(const nsAString& name, nsAString& _retval) final      \
   override                                                                    \

dom/interfaces/core/nsIDOMElement.idl

@@ -27,8 +27,6 @@ interface nsIDOMMozNamedAttrMap;
 [uuid(6289999b-1008-4269-b42a-413ec5a9d3f4)]
 interface nsIDOMElement : nsIDOMNode
 {
-  readonly attribute DOMString        tagName;
-
   DOMString          getAttribute(in DOMString name);
   void               setAttribute(in DOMString name, 
                                   in DOMString value);