diff --git a/content/html/content/src/HTMLProgressElement.cpp b/content/html/content/src/HTMLProgressElement.cpp
index e9aa9a040d4..6549fae1bc7 100644
--- a/content/html/content/src/HTMLProgressElement.cpp
+++ b/content/html/content/src/HTMLProgressElement.cpp
@@ -31,11 +31,8 @@ NS_IMPL_ADDREF_INHERITED(HTMLProgressElement, Element)
 NS_IMPL_RELEASE_INHERITED(HTMLProgressElement, Element)
 
 
-NS_INTERFACE_TABLE_HEAD(HTMLProgressElement)
+NS_INTERFACE_MAP_BEGIN(HTMLProgressElement)
   NS_HTML_CONTENT_INTERFACES(nsGenericHTMLElement)
-  NS_INTERFACE_TABLE_INHERITED1(HTMLProgressElement,
-                                nsIDOMHTMLProgressElement)
-  NS_INTERFACE_TABLE_TO_MAP_SEGUE
 NS_ELEMENT_INTERFACE_MAP_END
 
 NS_IMPL_ELEMENT_CLONE(HTMLProgressElement)
@@ -67,13 +64,6 @@ HTMLProgressElement::ParseAttribute(int32_t aNamespaceID, nsIAtom* aAttribute,
                                               aValue, aResult);
 }
 
-NS_IMETHODIMP
-HTMLProgressElement::GetValue(double* aValue)
-{
-  *aValue = Value();
-  return NS_OK;
-}
-
 double
 HTMLProgressElement::Value() const
 {
@@ -86,21 +76,6 @@ HTMLProgressElement::Value() const
   return std::min(attrValue->GetDoubleValue(), Max());
 }
 
-NS_IMETHODIMP
-HTMLProgressElement::SetValue(double aValue)
-{
-  ErrorResult rv;
-  SetValue(aValue, rv);
-  return rv.ErrorCode();
-}
-
-NS_IMETHODIMP
-HTMLProgressElement::GetMax(double* aValue)
-{
-  *aValue = Max();
-  return NS_OK;
-}
-
 double
 HTMLProgressElement::Max() const
 {
@@ -113,21 +88,6 @@ HTMLProgressElement::Max() const
   return attrMax->GetDoubleValue();
 }
 
-NS_IMETHODIMP
-HTMLProgressElement::SetMax(double aValue)
-{
-  ErrorResult rv;
-  SetMax(aValue, rv);
-  return rv.ErrorCode();
-}
-
-NS_IMETHODIMP
-HTMLProgressElement::GetPosition(double* aPosition)
-{
-  *aPosition = Position();
-  return NS_OK;
-}
-
 double
 HTMLProgressElement::Position() const
 {
diff --git a/content/html/content/src/HTMLProgressElement.h b/content/html/content/src/HTMLProgressElement.h
index 0be9491a8d8..985a1c3fee5 100644
--- a/content/html/content/src/HTMLProgressElement.h
+++ b/content/html/content/src/HTMLProgressElement.h
@@ -7,7 +7,6 @@
 #define mozilla_dom_HTMLProgressElement_h
 
 #include "mozilla/Attributes.h"
-#include "nsIDOMHTMLProgressElement.h"
 #include "nsGenericHTMLElement.h"
 #include "nsAttrValue.h"
 #include "nsAttrValueInlines.h"
@@ -18,7 +17,7 @@ namespace mozilla {
 namespace dom {
 
 class HTMLProgressElement MOZ_FINAL : public nsGenericHTMLElement,
-                                      public nsIDOMHTMLProgressElement
+                                      public nsIDOMHTMLElement
 {
 public:
   HTMLProgressElement(already_AddRefed<nsINodeInfo> aNodeInfo);
@@ -36,9 +35,6 @@ public:
   // nsIDOMHTMLElement
   NS_FORWARD_NSIDOMHTMLELEMENT_TO_GENERIC
 
-  // nsIDOMHTMLProgressElement
-  NS_DECL_NSIDOMHTMLPROGRESSELEMENT
-
   nsEventStates IntrinsicState() const MOZ_OVERRIDE;
 
   nsresult Clone(nsINodeInfo* aNodeInfo, nsINode** aResult) const MOZ_OVERRIDE;
diff --git a/dom/interfaces/html/moz.build b/dom/interfaces/html/moz.build
index e58d46cbac6..67def7b987f 100644
--- a/dom/interfaces/html/moz.build
+++ b/dom/interfaces/html/moz.build
@@ -55,7 +55,6 @@ XPIDL_SOURCES += [
     'nsIDOMHTMLParagraphElement.idl',
     'nsIDOMHTMLParamElement.idl',
     'nsIDOMHTMLPreElement.idl',
-    'nsIDOMHTMLProgressElement.idl',
     'nsIDOMHTMLQuoteElement.idl',
     'nsIDOMHTMLScriptElement.idl',
     'nsIDOMHTMLSelectElement.idl',
diff --git a/dom/interfaces/html/nsIDOMHTMLProgressElement.idl b/dom/interfaces/html/nsIDOMHTMLProgressElement.idl
deleted file mode 100644
index bd14c078cb4..00000000000
--- a/dom/interfaces/html/nsIDOMHTMLProgressElement.idl
+++ /dev/null
@@ -1,29 +0,0 @@
-/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsIDOMHTMLElement.idl"
-
-/**
- * The nsIDOMHTMLProgressElement interface is the interface to a HTML
- * <progress> element.
- *
- * For more information on this interface, please see
- * http://www.whatwg.org/specs/web-apps/current-work/#the-progress-element
- *
- * @status UNDER_DEVELOPMENT
- */
-
-[scriptable, uuid(4b4bec16-c65f-4a08-97d1-dff624efdca4)]
-interface nsIDOMHTMLProgressElement : nsIDOMHTMLElement
-{
-           attribute double value;
-           attribute double max;
-  readonly attribute double position;
-  /**
-   * The labels attribute will be done with bug 567740.
-   */
-  //readonly attribute NodeList labels;
-};
-
diff --git a/layout/forms/nsProgressFrame.cpp b/layout/forms/nsProgressFrame.cpp
index 139b643dba3..25e9e3e25d9 100644
--- a/layout/forms/nsProgressFrame.cpp
+++ b/layout/forms/nsProgressFrame.cpp
@@ -5,7 +5,6 @@
 
 #include "nsProgressFrame.h"
 
-#include "nsIDOMHTMLProgressElement.h"
 #include "nsIContent.h"
 #include "nsPresContext.h"
 #include "nsGkAtoms.h"
@@ -20,9 +19,11 @@
 #include "nsContentList.h"
 #include "nsFontMetrics.h"
 #include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLProgressElement.h"
 #include "nsContentList.h"
 #include <algorithm>
 
+using namespace mozilla::dom;
 
 nsIFrame*
 NS_NewProgressFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
@@ -157,10 +158,7 @@ nsProgressFrame::ReflowBarFrame(nsIFrame*                aBarFrame,
   nscoord xoffset = aReflowState.mComputedBorderPadding.left;
   nscoord yoffset = aReflowState.mComputedBorderPadding.top;
 
-  double position;
-  nsCOMPtr<nsIDOMHTMLProgressElement> progressElement =
-    do_QueryInterface(mContent);
-  progressElement->GetPosition(&position);
+  double position = static_cast<HTMLProgressElement*>(mContent)->Position();
 
   // Force the bar's size to match the current progress.
   // When indeterminate, the progress' size will be 100%.
diff --git a/widget/xpwidgets/nsNativeTheme.cpp b/widget/xpwidgets/nsNativeTheme.cpp
index ad272f8e4fc..2dfe2d241ab 100644
--- a/widget/xpwidgets/nsNativeTheme.cpp
+++ b/widget/xpwidgets/nsNativeTheme.cpp
@@ -14,7 +14,6 @@
 #include "nsString.h"
 #include "nsINameSpaceManager.h"
 #include "nsIDOMHTMLInputElement.h"
-#include "nsIDOMHTMLProgressElement.h"
 #include "nsIDOMXULMenuListElement.h"
 #include "nsThemeConstants.h"
 #include "nsIComponentManager.h"
@@ -26,9 +25,12 @@
 #include "nsCSSRendering.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/HTMLBodyElement.h"
+#include "mozilla/dom/HTMLProgressElement.h"
 #include "nsIDocumentInlines.h"
 #include <algorithm>
 
+using namespace mozilla::dom;
+
 nsNativeTheme::nsNativeTheme()
 : mAnimatedContentTimeout(UINT32_MAX)
 {
@@ -150,14 +152,8 @@ nsNativeTheme::GetProgressValue(nsIFrame* aFrame)
 {
   // When we are using the HTML progress element,
   // we can get the value from the IDL property.
-  if (aFrame) {
-    nsCOMPtr<nsIDOMHTMLProgressElement> progress =
-      do_QueryInterface(aFrame->GetContent());
-    if (progress) {
-      double value;
-      progress->GetValue(&value);
-      return value;
-    }
+  if (aFrame && aFrame->GetContent()->IsHTML(nsGkAtoms::progress)) {
+    return static_cast<HTMLProgressElement*>(aFrame->GetContent())->Value();
   }
 
   return (double)nsNativeTheme::CheckIntAttr(aFrame, nsGkAtoms::value, 0);
@@ -169,14 +165,8 @@ nsNativeTheme::GetProgressMaxValue(nsIFrame* aFrame)
 {
   // When we are using the HTML progress element,
   // we can get the max from the IDL property.
-  if (aFrame) {
-    nsCOMPtr<nsIDOMHTMLProgressElement> progress =
-      do_QueryInterface(aFrame->GetContent());
-    if (progress) {
-      double max;
-      progress->GetMax(&max);
-      return max;
-    }
+  if (aFrame && aFrame->GetContent()->IsHTML(nsGkAtoms::progress)) {
+    return static_cast<HTMLProgressElement*>(aFrame->GetContent())->Max();
   }
 
   return (double)std::max(nsNativeTheme::CheckIntAttr(aFrame, nsGkAtoms::max, 100), 1);