Bug 1634585: Return a rejected promise instead of nullptr from mozilla::GetProcInfo on Android; r=geckoview-reviewers,agi

This is a simple fix to eliminate crashing. Proper implementation of this
function will be done in bug 1529510.

Differential Revision: https://phabricator.services.mozilla.com/D76269

widget/android/ProcInfo.cpp

@@ -13,7 +13,7 @@ RefPtr<ProcInfoPromise> GetProcInfo(base::ProcessId pid, int32_t childId,
                                     const ProcType& type,
                                     const nsAString& origin) {
   // Not implemented on Android.
-  return nullptr;
+  return ProcInfoPromise::CreateAndReject(NS_ERROR_NOT_IMPLEMENTED, __func__);
 }
 
 }  // namespace mozilla