--- a/dom/base/nsJSUtils.cpp
+++ b/dom/base/nsJSUtils.cpp
@@ -22,16 +22,18 @@
 #include "nsPIDOMWindow.h"
 #include "GeckoProfiler.h"
 #include "nsDOMJSUtils.h" // for GetScriptContextFromJSContext
 #include "nsJSPrincipals.h"
 #include "xpcpublic.h"
 #include "nsContentUtils.h"
 #include "nsGlobalWindow.h"
 
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/ScriptSettings.h"
 
 using namespace mozilla::dom;
 
 bool
 nsJSUtils::GetCallingLocation(JSContext* aContext, const char* *aFilename,
                               uint32_t* aLineno)
 {
@@ -308,16 +310,37 @@ nsJSUtils::EvaluateString(JSContext* aCx
 {
   EvaluateOptions options;
   options.setNeedResult(false);
   JS::RootedValue unused(aCx);
   return EvaluateString(aCx, aSrcBuf, aScopeObject, aCompileOptions,
                         options, &unused, aOffThreadToken);
 }
 
+/* static */
+bool
+nsJSUtils::GetScopeChainForElement(JSContext* aCx,
+                                   mozilla::dom::Element* aElement,
+                                   JS::AutoObjectVector& aScopeChain)
+{
+  for (nsINode* cur = aElement; cur; cur = cur->GetScopeChainParent()) {
+    JS::RootedValue val(aCx);
+    if (!WrapNewBindingObject(aCx, cur, &val)) {
+      return false;
+    }
+
+    if (!aScopeChain.append(&val.toObject())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+
 //
 // nsDOMJSUtils.h
 //
 
 JSObject* GetDefaultScopeFromJSContext(JSContext *cx)
 {
   // DOM JSContexts don't store their default compartment object on
   // the cx, so in those cases we need to fetch it via the scx

--- a/dom/base/nsJSUtils.h
+++ b/dom/base/nsJSUtils.h
@@ -20,16 +20,17 @@
 #include "nsString.h"
 
 class nsIScriptContext;
 class nsIScriptGlobalObject;
 
 namespace mozilla {
 namespace dom {
 class AutoJSAPI;
+class Element;
 }
 }
 
 class nsJSUtils
 {
 public:
   static bool GetCallingLocation(JSContext* aContext, const char* *aFilename,
                                  uint32_t* aLineno);
@@ -114,16 +115,21 @@ public:
                                  void **aOffThreadToken = nullptr);
 
   static nsresult EvaluateString(JSContext* aCx,
                                  JS::SourceBufferHolder& aSrcBuf,
                                  JS::Handle<JSObject*> aScopeObject,
                                  JS::CompileOptions &aCompileOptions,
                                  void **aOffThreadToken = nullptr);
 
+  // Returns false if an exception got thrown on aCx.  Passing a null
+  // aElement is allowed; that wil produce an empty aScopeChain.
+  static bool GetScopeChainForElement(JSContext* aCx,
+                                      mozilla::dom::Element* aElement,
+                                      JS::AutoObjectVector& aScopeChain);
 };
 
 class MOZ_STACK_CLASS AutoDontReportUncaught {
   JSContext* mContext;
   bool mWasSet;
 
 public:
   explicit AutoDontReportUncaught(JSContext* aContext) : mContext(aContext) {