From 644beaf30bfedf45a6fdbb31a833532c672ba593 Mon Sep 17 00:00:00 2001
From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Thu, 30 Oct 2014 17:40:09 -0400
Subject: [PATCH] Bug 1088228 part 2.  Create an nsJSUtils API for building the
 scope chain for a given Element.  r=peterv

---
 dom/base/nsJSUtils.cpp | 23 +++++++++++++++++++++++
 dom/base/nsJSUtils.h   |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/dom/base/nsJSUtils.cpp b/dom/base/nsJSUtils.cpp
index 0132b4fc94c8..ddfb5bb084f8 100644
--- a/dom/base/nsJSUtils.cpp
+++ b/dom/base/nsJSUtils.cpp
@@ -27,6 +27,8 @@
 #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;
@@ -313,6 +315,27 @@ nsJSUtils::EvaluateString(JSContext* aCx,
                         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
 //
diff --git a/dom/base/nsJSUtils.h b/dom/base/nsJSUtils.h
index d46a5a5b09dd..3442487229ff 100644
--- a/dom/base/nsJSUtils.h
+++ b/dom/base/nsJSUtils.h
@@ -25,6 +25,7 @@ class nsIScriptGlobalObject;
 namespace mozilla {
 namespace dom {
 class AutoJSAPI;
+class Element;
 }
 }
 
@@ -119,6 +120,11 @@ public:
                                  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 {