Bug 1788596 - Remove extra lock() on UtilityProcessChild r=nika

Differential Revision: https://phabricator.services.mozilla.com/D156482

ipc/glue/UtilityProcessChild.cpp

@@ -45,14 +45,13 @@ static StaticRefPtr<UtilityProcessChild> sUtilityProcessChild;
 
 UtilityProcessChild::UtilityProcessChild() {
   nsDebugImpl::SetMultiprocessMode("Utility");
-  StaticMutexAutoLock lock(sUtilityProcessChildMutex);
-  sUtilityProcessChild = this;
 }
 
 UtilityProcessChild::~UtilityProcessChild() = default;
 
 /* static */
 RefPtr<UtilityProcessChild> UtilityProcessChild::GetSingleton() {
+  MOZ_ASSERT(XRE_IsUtilityProcess());
   StaticMutexAutoLock lock(sUtilityProcessChildMutex);
   if (!sUtilityProcessChild) {
     sUtilityProcessChild = new UtilityProcessChild();

ipc/glue/UtilityProcessImpl.h

@@ -27,7 +27,7 @@ class UtilityProcessImpl final : public ipc::ProcessChild {
   void CleanUp() override;
 
  private:
-  RefPtr<UtilityProcessChild> mUtility = new UtilityProcessChild();
+  RefPtr<UtilityProcessChild> mUtility = UtilityProcessChild::GetSingleton();
 
 #if defined(XP_WIN)
   mozilla::mscom::ProcessRuntime mCOMRuntime;