Bug 1775499 - check for null GetParentObject in Performance::Measure.…

… r=sefeng

Root cause: the global object can be null but I wasn't checking for it so it
caused a crash. I don't remember under what conditions it can be null but I saw
I had checked for null when I wrote Performance::Mark and remember debugging it
so it makes sense to do so here as well.

Differential Revision: https://phabricator.services.mozilla.com/D151960

dom/performance/Performance.cpp

@@ -528,6 +528,11 @@ already_AddRefed<PerformanceMeasure> Performance::Measure(
     JSContext* aCx, const nsAString& aName,
     const StringOrPerformanceMeasureOptions& aStartOrMeasureOptions,
     const Optional<nsAString>& aEndMark, ErrorResult& aRv) {
+  if (!GetParentObject()) {
+    aRv.ThrowInvalidStateError("Global object is unavailable");
+    return nullptr;
+  }
+
   // When resisting fingerprinting, we don't add marks to the buffer. Since
   // measure relies on relationships between marks in the buffer, this method
   // will throw if we look for user-entered marks so we return a dummy measure