--- a/browser/devtools/debugger/test/browser_dbg_propertyview-11.js
+++ b/browser/devtools/debugger/test/browser_dbg_propertyview-11.js
@@ -182,17 +182,17 @@ function testFrameParameters()
             "Should have the right property name for 'type' in buttonProtoNode.");
           is(buttonProtoNode.get("type").target.querySelector(".value")
              .getAttribute("value"), '"submit"',
             "'type' in buttonProtoNode should have the right value.");
           is(buttonProtoNode.get("formMethod").target.querySelector(".name")
              .getAttribute("value"), "formMethod",
             "Should have the right property name for 'formMethod' in buttonProtoNode.");
           is(buttonProtoNode.get("formMethod").target.querySelector(".value")
-             .getAttribute("value"), '"get"',
+             .getAttribute("value"), '""',
             "'formMethod' in buttonProtoNode should have the right value.");
 
           is(documentProtoNode.get("baseURI").target.querySelector(".name")
              .getAttribute("value"), "baseURI",
             "Should have the right property name for 'baseURI' in documentProtoNode.");
           is(documentProtoNode.get("baseURI").target.querySelector(".value")
              .getAttribute("value"), '"' + TAB_URL + '"',
             "'baseURI' in documentProtoNode should have the right value.");
@@ -238,17 +238,17 @@ function testFrameParameters()
               "Should have the right property name for 'type' in buttonAsProtoProtoProtoNode.");
             is(buttonAsProtoProtoProtoNode.get("type").target.querySelector(".value")
                .getAttribute("value"), '"submit"',
               "'type' in buttonAsProtoProtoProtoNode should have the right value.");
             is(buttonAsProtoProtoProtoNode.get("formMethod").target.querySelector(".name")
                .getAttribute("value"), "formMethod",
               "Should have the right property name for 'formMethod' in buttonAsProtoProtoProtoNode.");
             is(buttonAsProtoProtoProtoNode.get("formMethod").target.querySelector(".value")
-               .getAttribute("value"), '"get"',
+               .getAttribute("value"), '""',
               "'formMethod' in buttonAsProtoProtoProtoNode should have the right value.");
 
             resumeAndFinish();
           }, 100);
         }, 100);
       }, 100);
     }}, 0);
   }, false);

--- a/content/html/content/src/HTMLButtonElement.cpp
+++ b/content/html/content/src/HTMLButtonElement.cpp
@@ -114,20 +114,20 @@ NS_IMETHODIMP
 HTMLButtonElement::GetForm(nsIDOMHTMLFormElement** aForm)
 {
   return nsGenericHTMLFormElement::GetForm(aForm);
 }
 
 NS_IMPL_BOOL_ATTR(HTMLButtonElement, Autofocus, autofocus)
 NS_IMPL_BOOL_ATTR(HTMLButtonElement, Disabled, disabled)
 NS_IMPL_ACTION_ATTR(HTMLButtonElement, FormAction, formaction)
-NS_IMPL_ENUM_ATTR_DEFAULT_VALUE(HTMLButtonElement, FormEnctype, formenctype,
-                                kFormDefaultEnctype->tag)
-NS_IMPL_ENUM_ATTR_DEFAULT_VALUE(HTMLButtonElement, FormMethod, formmethod,
-                                kFormDefaultMethod->tag)
+NS_IMPL_ENUM_ATTR_DEFAULT_MISSING_INVALID_VALUES(HTMLButtonElement, FormEnctype, formenctype,
+                                                 "", kFormDefaultEnctype->tag)
+NS_IMPL_ENUM_ATTR_DEFAULT_MISSING_INVALID_VALUES(HTMLButtonElement, FormMethod, formmethod,
+                                                 "", kFormDefaultMethod->tag)
 NS_IMPL_BOOL_ATTR(HTMLButtonElement, FormNoValidate, formnovalidate)
 NS_IMPL_STRING_ATTR(HTMLButtonElement, FormTarget, formtarget)
 NS_IMPL_STRING_ATTR(HTMLButtonElement, Name, name)
 NS_IMPL_STRING_ATTR(HTMLButtonElement, Value, value)
 NS_IMPL_ENUM_ATTR_DEFAULT_VALUE(HTMLButtonElement, Type, type,
                                 kButtonDefaultType->tag)
 
 int32_t

--- a/content/html/content/test/Makefile.in
+++ b/content/html/content/test/Makefile.in
@@ -154,17 +154,16 @@ MOCHITEST_FILES = \
 		test_bug564001.html \
 		test_bug566046.html \
 		test_bug567938-1.html \
 		test_bug567938-2.html \
 		test_bug567938-3.html \
 		test_bug567938-4.html \
 		test_bug569955.html \
 		test_bug573969.html \
-		test_bug585508.html \
 		test_bug561640.html \
 		test_bug566064.html \
 		test_bug582412-1.html \
 		test_bug582412-2.html \
 		test_bug558788-1.html \
 		test_bug558788-2.html \
 		test_bug561634.html \
 		test_bug590353-1.html \

--- a/content/html/content/test/forms/test_button_attributes_reflection.html
+++ b/content/html/content/test/forms/test_button_attributes_reflection.html
@@ -35,37 +35,33 @@ reflectLimitedEnumerated({
   element: document.createElement("button"),
   attribute: "formEnctype",
   validValues: [
     "application/x-www-form-urlencoded",
     "multipart/form-data",
     "text/plain",
   ],
   invalidValues: [ "text/html", "", "tulip" ],
-// TODO (Bug 839171):
-//  defaultValue: {
-//    invalid: "application/x-www-form-urlencoded",
-//    missing: "",
-//  }
-  defaultValue: "application/x-www-form-urlencoded",
+  defaultValue: {
+    invalid: "application/x-www-form-urlencoded",
+    missing: "",
+  }
 });
 
 // .formMethod
 reflectLimitedEnumerated({
   element: document.createElement("button"),
   attribute: "formMethod",
   validValues: [ "get", "post" ],
   invalidValues: [ "put", "", "tulip" ],
   unsupportedValues: [ "dialog" ],
-// TODO (Bug 839171):
-//  defaultValue: {
-//    invalid: "get",
-//    missing: "",
-//  }
-  defaultValue: "get",
+  defaultValue: {
+    invalid: "get",
+    missing: "",
+  }
 });
 
 // .formNoValidate
 reflectBoolean({
   element: document.createElement("button"),
   attribute: "formNoValidate",
 });
 

deleted file mode 100644
--- a/content/html/content/test/test_bug585508.html
+++ /dev/null
@@ -1,72 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=585508
--->
-<head>
-  <title>Test for Bug 585508</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=585508">Mozilla Bug 585508</a>
-<p id="display"></p>
-<pre id="test">
-<script type="application/javascript">
-
-/** Test for Bug 585508 **/
-
-var enctypeTestData = [
-  // Default value.
-  [ "application/x-www-form-urlencoded" ],
-  // Valid values.
-  [ "application/x-www-form-urlencoded", "multipart/form-data", "text/plain" ],
-  // Invalid values.
-  [ "", " ", "foo", "multipart/foo" ]
-];
-
-var methodTestData = [
-  // Default value.
-  [ "get" ],
-  // Valid values.
-  [ "get", "post" ],
-  // Invalid values.
-  [ "", " ", "foo" ],
-];
-
-function checkAttribute(form, attrName, idlName, data)
-{
-  is(form.getAttribute(attrName), null,
-     "By default " + attrName + " content attribute should be null");
-  is(form[idlName], data[0][0],
-     "By default " + idlName + " IDL attribute should be equal to " +
-     data[0][0]);
-
-  // Valid values.
-  for (i in data[1]) {
-    form.setAttribute(attrName, data[1][i]);
-    is(form.getAttribute(attrName), data[1][i],
-       "getAttribute should return the content attribute");
-    is(form[idlName], data[1][i], "When getting, " + idlName + " IDL attribute " +
-       "should be equal to the content attribute if the value is known");
-  }
-
-  // Invalid values.
-  for (i in data[2]) {
-    form.setAttribute(attrName, data[2][i]);
-    is(form.getAttribute(attrName), data[2][i],
-       "getAttribute should return the content attribute");
-    is(form[idlName], data[0][0], "When getting, " + idlName + " IDL attribute " +
-       "should return the default value if the content attribute value isn't known");
-  }
-}
-
-var button = document.createElement('button');
-
-checkAttribute(button, 'formenctype', 'formEnctype', enctypeTestData);
-checkAttribute(button, 'formmethod', 'formMethod', methodTestData);
-
-</script>
-</pre>
-</body>
-</html>