Bug 1418085 part 4. Stop using nsIDOMHTMLElement in JS code. r=mystor

MozReview-Commit-ID: GsSnXNXGrHg

devtools/server/actors/object.js

@@ -1853,11 +1853,15 @@ DebuggerServer.ObjectActorPreviewers.Object = [
         }
       }
     } else if (rawObj instanceof Ci.nsIDOMElement) {
-      // Add preview for DOM element attributes.
-      if (rawObj instanceof Ci.nsIDOMHTMLElement) {
+      // For HTML elements (in an HTML document, at least), the nodeName is an
+      // uppercased version of the actual element name.  Check for HTML
+      // elements, that is elements in the HTML namespace, and lowercase the
+      // nodeName in that case.
+      if (rawObj.namespaceURI == "http://www.w3.org/1999/xhtml") {
         preview.nodeName = preview.nodeName.toLowerCase();
       }
 
+      // Add preview for DOM element attributes.
       preview.attributes = {};
       preview.attributesLength = rawObj.attributes.length;
       for (let attr of rawObj.attributes) {

dom/html/test/test_bug389797.html

@@ -41,10 +41,6 @@ function HTML_TAG(aTagName, aImplClass) {
   var interfaceName = "nsIDOM" + getClassName(aTagName);
   if (interfaceName in SpecialPowers.Ci) {  // no nsIDOMHTMLSpanElement
     interfaces[aTagName].push(interfaceName);
-    interfacesNonClassinfo[aTagName].push("nsIDOMHTMLElement");
-  } else {
-    // Inherits directly from nsIDOMHTMLElement.
-    interfaces[aTagName].push("nsIDOMHTMLElement");
   }
 
   var interfaceNameNS = "nsIDOMNS" + getClassName(aTagName);