diff --git a/content/base/public/Element.h b/content/base/public/Element.h
index 0db53c6db269..9ad1cb314b93 100644
--- a/content/base/public/Element.h
+++ b/content/base/public/Element.h
@@ -725,9 +725,9 @@ public:
   {
   }
 
-  virtual void GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError);
+  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML);
   virtual void SetInnerHTML(const nsAString& aInnerHTML, ErrorResult& aError);
-  void GetOuterHTML(nsAString& aOuterHTML, ErrorResult& aError);
+  void GetOuterHTML(nsAString& aOuterHTML);
   void SetOuterHTML(const nsAString& aOuterHTML, ErrorResult& aError);
   void InsertAdjacentHTML(const nsAString& aPosition, const nsAString& aText,
                           ErrorResult& aError);
@@ -1124,7 +1124,7 @@ private:
   nsIScrollableFrame* GetScrollFrame(nsIFrame **aStyledFrame = nullptr,
                                      bool aFlushLayout = true);
 
-  nsresult GetMarkup(bool aIncludeSelf, nsAString& aMarkup);
+  void GetMarkup(bool aIncludeSelf, nsAString& aMarkup);
 
   // Data members
   nsEventStates mState;
diff --git a/content/base/src/Element.cpp b/content/base/src/Element.cpp
index 8ae70aea28a5..1f8f6f59ab38 100644
--- a/content/base/src/Element.cpp
+++ b/content/base/src/Element.cpp
@@ -3107,14 +3107,15 @@ Serialize(Element* aRoot, bool aDescendentsOnly, nsAString& aOut)
   }
 }
 
-nsresult
+void
 Element::GetMarkup(bool aIncludeSelf, nsAString& aMarkup)
 {
   aMarkup.Truncate();
 
   nsIDocument* doc = OwnerDoc();
   if (IsInHTMLDocument()) {
-    return Serialize(this, !aIncludeSelf, aMarkup) ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+    Serialize(this, !aIncludeSelf, aMarkup);
+    return;
   }
 
   nsAutoString contentType;
@@ -3135,7 +3136,7 @@ Element::GetMarkup(bool aIncludeSelf, nsAString& aMarkup)
     docEncoder = do_CreateInstance(NS_DOC_ENCODER_CONTRACTID_BASE "application/xml");
   }
 
-  NS_ENSURE_TRUE(docEncoder, NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE_VOID(docEncoder);
 
   uint32_t flags = nsIDocumentEncoder::OutputEncodeBasicEntities |
                    // Output DOM-standard newlines
@@ -3153,8 +3154,8 @@ Element::GetMarkup(bool aIncludeSelf, nsAString& aMarkup)
     }
   }
 
-  nsresult rv = docEncoder->NativeInit(doc, contentType, flags);
-  NS_ENSURE_SUCCESS(rv, rv);
+  DebugOnly<nsresult> rv = docEncoder->NativeInit(doc, contentType, flags);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
 
   if (aIncludeSelf) {
     docEncoder->SetNativeNode(this);
@@ -3162,10 +3163,10 @@ Element::GetMarkup(bool aIncludeSelf, nsAString& aMarkup)
     docEncoder->SetNativeContainerNode(this);
   }
   rv = docEncoder->EncodeToString(aMarkup);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
   if (!aIncludeSelf) {
     doc->SetCachedEncoder(docEncoder.forget());
   }
-  return rv;
 }
 
 /**
@@ -3197,10 +3198,11 @@ FireMutationEventsForDirectParsing(nsIDocument* aDoc, nsIContent* aDest,
   }
 }
 
-void
-Element::GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError)
+NS_IMETHODIMP
+Element::GetInnerHTML(nsAString& aInnerHTML)
 {
-  aError = GetMarkup(false, aInnerHTML);
+  GetMarkup(false, aInnerHTML);
+  return NS_OK;
 }
 
 void
@@ -3266,9 +3268,9 @@ Element::SetInnerHTML(const nsAString& aInnerHTML, ErrorResult& aError)
 }
 
 void
-Element::GetOuterHTML(nsAString& aOuterHTML, ErrorResult& aError)
+Element::GetOuterHTML(nsAString& aOuterHTML)
 {
-  aError = GetMarkup(true, aOuterHTML);
+  GetMarkup(true, aOuterHTML);
 }
 
 void
diff --git a/content/html/content/src/HTMLElement.cpp b/content/html/content/src/HTMLElement.cpp
index f6c675dc3bcb..3547fce499a2 100644
--- a/content/html/content/src/HTMLElement.cpp
+++ b/content/html/content/src/HTMLElement.cpp
@@ -16,9 +16,7 @@ public:
   HTMLElement(already_AddRefed<nsINodeInfo> aNodeInfo);
   virtual ~HTMLElement();
 
-  using nsGenericHTMLElement::GetInnerHTML;
-  virtual void GetInnerHTML(nsAString& aInnerHTML,
-                            mozilla::ErrorResult& aError) MOZ_OVERRIDE;
+  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML) MOZ_OVERRIDE;
 
   virtual nsresult Clone(nsINodeInfo* aNodeInfo,
                          nsINode** aResult) const MOZ_OVERRIDE;
@@ -39,8 +37,8 @@ HTMLElement::~HTMLElement()
 
 NS_IMPL_ELEMENT_CLONE(HTMLElement)
 
-void
-HTMLElement::GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError)
+NS_IMETHODIMP
+HTMLElement::GetInnerHTML(nsAString& aInnerHTML)
 {
   /**
    * nsGenericHTMLElement::GetInnerHTML escapes < and > characters (at least).
@@ -52,10 +50,10 @@ HTMLElement::GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError)
   if (mNodeInfo->Equals(nsGkAtoms::xmp) ||
       mNodeInfo->Equals(nsGkAtoms::plaintext)) {
     nsContentUtils::GetNodeTextContent(this, false, aInnerHTML);
-    return;
+    return NS_OK;
   }
 
-  nsGenericHTMLElement::GetInnerHTML(aInnerHTML, aError);
+  return nsGenericHTMLElement::GetInnerHTML(aInnerHTML);
 }
 
 JSObject*
diff --git a/content/html/content/src/HTMLScriptElement.cpp b/content/html/content/src/HTMLScriptElement.cpp
index 3ecd7b2fb7ca..1794d7b36eaf 100644
--- a/content/html/content/src/HTMLScriptElement.cpp
+++ b/content/html/content/src/HTMLScriptElement.cpp
@@ -226,10 +226,11 @@ HTMLScriptElement::AfterSetAttr(int32_t aNamespaceID, nsIAtom* aName,
                                             aNotify);
 }
 
-void
-HTMLScriptElement::GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError)
+NS_IMETHODIMP
+HTMLScriptElement::GetInnerHTML(nsAString& aInnerHTML)
 {
   nsContentUtils::GetNodeTextContent(this, false, aInnerHTML);
+  return NS_OK;
 }
 
 void
diff --git a/content/html/content/src/HTMLScriptElement.h b/content/html/content/src/HTMLScriptElement.h
index 20a8f4682936..6b950ae182e5 100644
--- a/content/html/content/src/HTMLScriptElement.h
+++ b/content/html/content/src/HTMLScriptElement.h
@@ -30,9 +30,7 @@ public:
   // nsISupports
   NS_DECL_ISUPPORTS_INHERITED
 
-  using nsGenericHTMLElement::GetInnerHTML;
-  virtual void GetInnerHTML(nsAString& aInnerHTML,
-                            mozilla::ErrorResult& aError) MOZ_OVERRIDE;
+  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML) MOZ_OVERRIDE;
   using nsGenericHTMLElement::SetInnerHTML;
   virtual void SetInnerHTML(const nsAString& aInnerHTML,
                             mozilla::ErrorResult& aError) MOZ_OVERRIDE;
diff --git a/content/html/content/src/HTMLStyleElement.cpp b/content/html/content/src/HTMLStyleElement.cpp
index 33f2e26e5f48..712c0425b571 100644
--- a/content/html/content/src/HTMLStyleElement.cpp
+++ b/content/html/content/src/HTMLStyleElement.cpp
@@ -201,10 +201,11 @@ HTMLStyleElement::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aAttribute,
   return rv;
 }
 
-void
-HTMLStyleElement::GetInnerHTML(nsAString& aInnerHTML, ErrorResult& aError)
+NS_IMETHODIMP
+HTMLStyleElement::GetInnerHTML(nsAString& aInnerHTML)
 {
   nsContentUtils::GetNodeTextContent(this, false, aInnerHTML);
+  return NS_OK;
 }
 
 void
diff --git a/content/html/content/src/HTMLStyleElement.h b/content/html/content/src/HTMLStyleElement.h
index cf981e027e7e..142c4ad3bfdb 100644
--- a/content/html/content/src/HTMLStyleElement.h
+++ b/content/html/content/src/HTMLStyleElement.h
@@ -33,9 +33,7 @@ public:
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(HTMLStyleElement,
                                            nsGenericHTMLElement)
 
-  using nsGenericHTMLElement::GetInnerHTML;
-  virtual void GetInnerHTML(nsAString& aInnerHTML,
-                            mozilla::ErrorResult& aError) MOZ_OVERRIDE;
+  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML) MOZ_OVERRIDE;
   using nsGenericHTMLElement::SetInnerHTML;
   virtual void SetInnerHTML(const nsAString& aInnerHTML,
                             mozilla::ErrorResult& aError) MOZ_OVERRIDE;
diff --git a/content/html/content/src/nsGenericHTMLElement.h b/content/html/content/src/nsGenericHTMLElement.h
index 4c6b59fb3bec..5598e58fb8dc 100644
--- a/content/html/content/src/nsGenericHTMLElement.h
+++ b/content/html/content/src/nsGenericHTMLElement.h
@@ -464,9 +464,8 @@ public:
     return rv.ErrorCode();
   }
   NS_IMETHOD GetOuterHTML(nsAString& aOuterHTML) MOZ_FINAL {
-    mozilla::ErrorResult rv;
-    mozilla::dom::Element::GetOuterHTML(aOuterHTML, rv);
-    return rv.ErrorCode();
+    mozilla::dom::Element::GetOuterHTML(aOuterHTML);
+    return NS_OK;
   }
   NS_IMETHOD SetOuterHTML(const nsAString& aOuterHTML) MOZ_FINAL {
     mozilla::ErrorResult rv;
@@ -528,11 +527,8 @@ public:
     *aDraggable = Draggable();
     return NS_OK;
   }
-  using mozilla::dom::Element::GetInnerHTML;
-  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML) MOZ_FINAL {
-    mozilla::ErrorResult rv;
-    GetInnerHTML(aInnerHTML, rv);
-    return rv.ErrorCode();
+  NS_IMETHOD GetInnerHTML(nsAString& aInnerHTML) MOZ_OVERRIDE {
+    return mozilla::dom::Element::GetInnerHTML(aInnerHTML);
   }
   using mozilla::dom::Element::SetInnerHTML;
   NS_IMETHOD SetInnerHTML(const nsAString& aInnerHTML) MOZ_FINAL {
diff --git a/dom/webidl/Element.webidl b/dom/webidl/Element.webidl
index dc1762702215..1a6cf6cef06f 100644
--- a/dom/webidl/Element.webidl
+++ b/dom/webidl/Element.webidl
@@ -175,9 +175,9 @@ partial interface Element {
 
 // http://domparsing.spec.whatwg.org/#extensions-to-the-element-interface
 partial interface Element {
-  [Throws,TreatNullAs=EmptyString]
+  [Pure,SetterThrows,TreatNullAs=EmptyString]
   attribute DOMString innerHTML;
-  [Throws,TreatNullAs=EmptyString]
+  [Pure,SetterThrows,TreatNullAs=EmptyString]
   attribute DOMString outerHTML;
   [Throws]
   void insertAdjacentHTML(DOMString position, DOMString text);