--- a/embedding/browser/nsDocShellTreeOwner.cpp
+++ b/embedding/browser/nsDocShellTreeOwner.cpp
@@ -71,21 +71,25 @@
 using namespace mozilla;
 using namespace mozilla::dom;
 
 // A helper routine that navigates the tricky path from a |nsWebBrowser| to
 // a |EventTarget| via the window root and chrome event handler.
 static nsresult
 GetDOMEventTarget(nsWebBrowser* aInBrowser, EventTarget** aTarget)
 {
-  NS_ENSURE_ARG_POINTER(aInBrowser);
+  if (!aInBrowser) {
+    return NS_ERROR_INVALID_POINTER;
+  }
 
   nsCOMPtr<nsIDOMWindow> domWindow;
   aInBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
-  NS_ENSURE_TRUE(domWindow, NS_ERROR_FAILURE);
+  if (!domWindow) {
+    return NS_ERROR_FAILURE;
+  }
 
   nsCOMPtr<nsPIDOMWindow> domWindowPrivate = do_QueryInterface(domWindow);
   NS_ENSURE_TRUE(domWindowPrivate, NS_ERROR_FAILURE);
   nsPIDOMWindow* rootWindow = domWindowPrivate->GetPrivateRoot();
   NS_ENSURE_TRUE(rootWindow, NS_ERROR_FAILURE);
   nsCOMPtr<EventTarget> target = rootWindow->GetChromeEventHandler();
   NS_ENSURE_TRUE(target, NS_ERROR_FAILURE);
   target.forget(aTarget);

--- a/embedding/browser/nsWebBrowser.cpp
+++ b/embedding/browser/nsWebBrowser.cpp
@@ -355,17 +355,20 @@ nsWebBrowser::SetParentURIContentListene
     return listener->SetParentContentListener(aParentContentListener);
   }
   return NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsWebBrowser::GetContentDOMWindow(nsIDOMWindow** aResult)
 {
-  NS_ENSURE_STATE(mDocShell);
+  if (!mDocShell) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
   nsCOMPtr<nsIDOMWindow> retval = mDocShell->GetWindow();
   retval.forget(aResult);
   return *aResult ? NS_OK : NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsWebBrowser::GetIsActive(bool* aResult)
 {