Bug 1547923 part 6. Make nsIGlobalObject::GetGlobalJSObject always expose to active JS. r=mccr8

See callsite audit in https://bugzilla.mozilla.org/attachment.cgi?id=9061976
for details on why the remaining GetGlobalJSObject callers should switch to the
"always expose" behavior.

Differential Revision: https://phabricator.services.mozilla.com/D29707

dom/script/ScriptSettings.cpp

@@ -297,7 +297,7 @@ void AutoJSAPI::InitInternal(nsIGlobalObject* aGlobalObject, JSObject* aGlobal,
   mIsMainThread = aIsMainThread;
   mGlobalObject = aGlobalObject;
   if (aGlobal) {
-    JS::ExposeObjectToActiveJS(aGlobal);
+    JS::AssertObjectIsNotGray(aGlobal);
   }
   mAutoNullableRealm.emplace(mCx, aGlobal);