Issue #1691 - Part 11: Fix incorrect reference counting in ModuleScript class.

(cherry picked from commit 4ef1fa98c9518f5c107424667229ddb6f9f97767)

dom/script/ModuleScript.cpp

@@ -132,6 +132,7 @@ ModuleScript::UnlinkModuleRecord()
                this);
     JS::SetModulePrivate(mModuleRecord, JS::UndefinedValue());
     mModuleRecord = nullptr;
+    Release();
   }
 }
 
@@ -156,6 +157,7 @@ ModuleScript::SetModuleRecord(JS::Handle<JSObject*> aModuleRecord)
   MOZ_ASSERT(JS::GetModulePrivate(mModuleRecord).isUndefined());
   JS::SetModulePrivate(mModuleRecord, JS::PrivateValue(this));
   HoldJSObjects(this);
+  AddRef();
 }
 
 void
@@ -168,7 +170,6 @@ ModuleScript::SetParseError(const JS::Value& aError)
   UnlinkModuleRecord();
   mParseError = aError;
   HoldJSObjects(this);
-  AddRef();
 }
 
 void