diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index c6c5a7c0db7..a2177bb11db 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -2886,6 +2886,13 @@ nsDocShell::GetParent(nsIDocShellTreeItem ** aParent)
     return NS_OK;
 }
 
+already_AddRefed<nsDocShell>
+nsDocShell::GetParentDocshell()
+{
+    nsCOMPtr<nsIDocShell> docshell = do_QueryInterface(GetAsSupports(mParent));
+    return static_cast<nsDocShell*>(docshell.forget().get());
+}
+
 nsresult
 nsDocShell::SetDocLoaderParent(nsDocLoader * aParent)
 {
@@ -12436,91 +12443,16 @@ nsDocShell::GetCanExecuteScripts(bool *aResult)
   NS_ENSURE_ARG_POINTER(aResult);
   *aResult = false; // disallow by default
 
-  nsCOMPtr<nsIDocShell> docshell = this;
-  nsCOMPtr<nsIDocShellTreeItem> globalObjTreeItem =
-      do_QueryInterface(docshell);
+  nsRefPtr<nsDocShell> docshell = this;
+  do {
+      nsresult rv = docshell->GetAllowJavascript(aResult);
+      if (NS_FAILED(rv)) return rv;
+      if (!*aResult) {
+          return NS_OK;
+      }
 
-  if (globalObjTreeItem)
-  {
-      nsCOMPtr<nsIDocShellTreeItem> treeItem(globalObjTreeItem);
-      nsCOMPtr<nsIDocShellTreeItem> parentItem;
-      bool firstPass = true;
-      bool lookForParents = false;
-
-      // Walk up the docshell tree to see if any containing docshell disallows scripts
-      do
-      {
-          nsresult rv = docshell->GetAllowJavascript(aResult);
-          if (NS_FAILED(rv)) return rv;
-          if (!*aResult) {
-              nsDocShell* realDocshell = static_cast<nsDocShell*>(docshell.get());
-              if (realDocshell->mContentViewer) {
-                  nsIDocument* doc = realDocshell->mContentViewer->GetDocument();
-                  if (doc && doc->HasFlag(NODE_IS_EDITABLE) &&
-                      realDocshell->mEditorData) {
-                      nsCOMPtr<nsIEditingSession> editSession;
-                      realDocshell->mEditorData->GetEditingSession(getter_AddRefs(editSession));
-                      bool jsDisabled = false;
-                      if (editSession &&
-                          NS_SUCCEEDED(rv = editSession->GetJsAndPluginsDisabled(&jsDisabled))) {
-                          if (firstPass) {
-                              if (jsDisabled) {
-                                  // We have a docshell which has been explicitly set
-                                  // to design mode, so we disallow scripts.
-                                  return NS_OK;
-                              }
-                              // The docshell was not explicitly set to design mode,
-                              // so it must be so because a parent was explicitly
-                              // set to design mode.  We don't need to look at higher
-                              // docshells.
-                              *aResult = true;
-                              break;
-                          } else if (lookForParents && jsDisabled) {
-                              // If a parent was explicitly set to design mode,
-                              // we should allow script execution on the child.
-                              *aResult = true;
-                              break;
-                          }
-                          // If the child docshell allows scripting, and the
-                          // parent is inside design mode, we don't need to look
-                          // further.
-                          *aResult = true;
-                          return NS_OK;
-                      }
-                      NS_WARNING("The editing session does not work?");
-                      return NS_FAILED(rv) ? rv : NS_ERROR_FAILURE;
-                  }
-                  if (firstPass) {
-                      // Don't be too hard on docshells on the first pass.
-                      // There may be a parent docshell which has been set
-                      // to design mode, so look for it.
-                      lookForParents = true;
-                  } else {
-                      // We have a docshell which disallows scripts
-                      // and is not editable, so we shouldn't allow
-                      // scripts at all.
-                      return NS_OK;
-                  }
-              }
-          } else if (lookForParents) {
-              // The parent docshell was not explicitly set to design
-              // mode, so js on the child docshell was disabled for
-              // another reason.  Therefore, we need to disable js.
-              *aResult = false;
-              return NS_OK;
-          }
-          firstPass = false;
-
-          treeItem->GetParent(getter_AddRefs(parentItem));
-          treeItem.swap(parentItem);
-          docshell = do_QueryInterface(treeItem);
-#ifdef DEBUG
-          if (treeItem && !docshell) {
-            NS_ERROR("cannot get a docshell from a treeItem!");
-          }
-#endif // DEBUG
-      } while (treeItem && docshell);
-  }
+      docshell = docshell->GetParentDocshell();
+  } while (docshell);
 
   return NS_OK;
 }
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index 5af0b08d754..588643b2081 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -643,6 +643,9 @@ protected:
     nsIChannel* GetCurrentDocChannel();
 
     bool ShouldBlockLoadingForBackButton();
+
+    // Convenience method for getting our parent docshell.  Can return null
+    already_AddRefed<nsDocShell> GetParentDocshell();
 protected:
     // Override the parent setter from nsDocLoader
     virtual nsresult SetDocLoaderParent(nsDocLoader * aLoader);
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index 994f0178290..c6e629c1e6f 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -528,10 +528,7 @@ interface nsIDocShell : nsIDocShellTreeItem
   /**
    * Whether this docshell can execute scripts based on its hierarchy.
    * The rule of thumb here is that we disable js if this docshell or any
-   * of its parents disallow scripting, unless the only reason for js being
-   * disabled in this docshell is a parent docshell having a document that
-   * is in design mode.  In that case, we explicitly allow scripting on the
-   * current docshell.
+   * of its parents disallow scripting.
    */
   readonly attribute boolean canExecuteScripts;
 
diff --git a/editor/composer/test/test_bug519928.html b/editor/composer/test/test_bug519928.html
index 71d5288bedf..545ec4551f0 100644
--- a/editor/composer/test/test_bug519928.html
+++ b/editor/composer/test/test_bug519928.html
@@ -65,7 +65,7 @@ addLoadEvent(function() {
                       expectJSAllowed(true, enterDesignMode, function() {
                         expectJSAllowed(true, leaveDesignMode, function() {
                           expectJSAllowed(false, disableJS, function() {
-                            expectJSAllowed(true, enterDesignMode, function() {
+                            expectJSAllowed(false, enterDesignMode, function() {
                               expectJSAllowed(false, leaveDesignMode, function() {
                                 expectJSAllowed(true, enableJS, function() {
                                   testDocumentDisabledJS();
@@ -94,7 +94,7 @@ function testDocumentDisabledJS() {
   document.designMode = "off";
   iframe.contentDocument.designMode = "off";
 
-  // Javascriont enabled on the main iframe
+  // Javascript enabled on the main iframe
   enableJS();
 
   var doc = iframe.contentDocument;