--- a/dom/bindings/BindingDeclarations.h
+++ b/dom/bindings/BindingDeclarations.h
@@ -29,20 +29,18 @@ class nsWrapperCache;
 class nsGlobalWindow;
 
 namespace mozilla {
 namespace dom {
 
 struct MainThreadDictionaryBase
 {
 protected:
-  JSContext* ParseJSON(const nsAString& aJSON,
-                       Maybe<JSAutoRequest>& aAr,
-                       Maybe<JSAutoCompartment>& aAc,
-                       Maybe< JS::Rooted<JS::Value> >& aVal);
+  bool ParseJSON(JSContext *aCx, const nsAString& aJSON,
+                 JS::MutableHandle<JS::Value> aVal);
 };
 
 struct EnumEntry {
   const char* value;
   size_t length;
 };
 
 class MOZ_STACK_CLASS GlobalObject

--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -1306,36 +1306,27 @@ SetXrayExpandoChain(JSObject* obj, JSObj
     MOZ_ASSERT(js::GetProxyHandler(obj)->family() == ProxyFamily());
     js::SetProxyExtra(obj, JSPROXYSLOT_XRAY_EXPANDO, v);
   } else {
     MOZ_ASSERT(JS_IsNativeFunction(obj, Constructor));
     js::SetFunctionNativeReserved(obj, CONSTRUCTOR_XRAY_EXPANDO_SLOT, v);
   }
 }
 
-JSContext*
-MainThreadDictionaryBase::ParseJSON(const nsAString& aJSON,
-                                    Maybe<JSAutoRequest>& aAr,
-                                    Maybe<JSAutoCompartment>& aAc,
-                                    Maybe< JS::Rooted<JS::Value> >& aVal)
+bool
+MainThreadDictionaryBase::ParseJSON(JSContext *aCx,
+                                    const nsAString& aJSON,
+                                    JS::MutableHandle<JS::Value> aVal)
 {
-  AutoSafeJSContext cx;
-  JS::Rooted<JSObject*> global(cx, JS_GetGlobalObject(cx));
-  aAr.construct(static_cast<JSContext*>(cx));
-  aAc.construct(static_cast<JSContext*>(cx), global);
-  aVal.construct(static_cast<JSContext*>(cx), JS::UndefinedValue());
   if (aJSON.IsEmpty()) {
-    return cx;
+    return true;
   }
-  if (!JS_ParseJSON(cx,
-                    static_cast<const jschar*>(PromiseFlatString(aJSON).get()),
-                    aJSON.Length(), aVal.ref().address())) {
-    return nullptr;
-  }
-  return cx;
+  return JS_ParseJSON(aCx,
+                      static_cast<const jschar*>(PromiseFlatString(aJSON).get()),
+                      aJSON.Length(), aVal.address());
 }
 
 static JSString*
 ConcatJSString(JSContext* cx, const char* pre, JSString* str, const char* post)
 {
   if (!str) {
     return nullptr;
   }

--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -7345,29 +7345,20 @@ class CGDictionary(CGThing):
         memberDecls = ["  %s %s;" %
                        (self.getMemberType(m),
                         self.makeMemberName(m[0].identifier.name))
                        for m in self.memberInfo]
 
         return (string.Template(
                 "struct ${selfName} ${inheritance}{\n"
                 "  ${selfName}() {}\n"
-                "  bool Init(JSContext* cx, JS::Handle<JS::Value> val);\n"
+                "  bool Init(JSContext* cx, JS::Handle<JS::Value> val);\n" +
+                ("  bool Init(const nsAString& aJSON);\n" if not self.workers else "") +
                 "  bool ToObject(JSContext* cx, JS::Handle<JSObject*> parentObject, JS::Value *vp) const;\n"
                 "\n" +
-                ("  bool Init(const nsAString& aJSON)\n"
-                 "  {\n"
-                 "    Maybe<JSAutoRequest> ar;\n"
-                 "    Maybe<JSAutoCompartment> ac;\n"
-                 "    Maybe< JS::Rooted<JS::Value> > json;\n"
-                 "    JSContext* cx = ParseJSON(aJSON, ar, ac, json);\n"
-                 "    NS_ENSURE_TRUE(cx, false);\n"
-                 "    return Init(cx, json.ref());\n"
-                 "  }\n" if not self.workers else "") +
-                "\n" +
                 "\n".join(memberDecls) + "\n"
                 "private:\n"
                 "  // Disallow copy-construction\n"
                 "  ${selfName}(const ${selfName}&) MOZ_DELETE;\n" +
                 # NOTE: jsids are per-runtime, so don't use them in workers
                 ("  static bool InitIds(JSContext* cx);\n"
                  "  static bool initedIds;\n" if self.needToInitIds else "") +
                 "\n".join("  static jsid " +
@@ -7449,16 +7440,27 @@ class CGDictionary(CGThing):
              "  bool isNull = val.isNullOrUndefined();\n" if len(memberInits) > 0 else "") +
             "  if (!IsConvertibleToDictionary(cx, val)) {\n"
             "    return ThrowErrorMessage(cx, MSG_NOT_DICTIONARY);\n"
             "  }\n"
             "\n"
             "${initMembers}\n"
             "  return true;\n"
             "}\n"
+            "\n" +
+            ("bool\n"
+             "${selfName}::Init(const nsAString& aJSON)\n"
+             "{\n"
+             "  AutoSafeJSContext cx;\n"
+             "  JSAutoRequest ar(cx);\n"
+             "  JS::Rooted<JS::Value> json(cx);\n"
+             "  bool ok = ParseJSON(cx, aJSON, &json);\n"
+             "  NS_ENSURE_TRUE(ok, false);\n"
+             "  return Init(cx, json);\n"
+             "}\n" if not self.workers else "") +
             "\n"
             "bool\n"
             "${selfName}::ToObject(JSContext* cx, JS::Handle<JSObject*> parentObject, JS::Value *vp) const\n"
             "{\n" +
             # NOTE: jsids are per-runtime, so don't use them in workers
             ("  if (!initedIds && !InitIds(cx)) {\n"
              "    return false;\n"
              "  }\n" if self.needToInitIds else "") +