Bug 1914602 - Stop preloading Mozilla DLLs for WMF software encoding in content process. r=bobowen

We currently preload these DLLs in all content processes, which
presumably has some performance impact. We did this in bug 1910861 to
mitigate the crashes with ESET from bug 1905690 - but ESET has since
then pushed new changes that perhaps will fix the crashes. If not, we
want to mitigate the crashes in another way that does not involve
preloading the DLLs in all content processes. Preloading is not required
even with sandbox level 8, because we already allow access to the bin
dir anyway.

Differential Revision: https://phabricator.services.mozilla.com/D219961

dom/ipc/ContentChild.cpp

@@ -1732,13 +1732,6 @@ mozilla::ipc::IPCResult ContentChild::RecvSetProcessSandbox(
         ContentProcessSandboxParams::ForThisProcess(aBroker));
   }
 #  elif defined(XP_WIN)
-  // Mozilla libraries that are required for WMF software encoding. We preload
-  // them here - where failure is non-fatal - to let third-party software
-  // discover them early after an update. We thereby mitigate fatal failures
-  // elsewhere (bug 1905690).
-  ::LoadLibraryW(L"mozavcodec.dll");
-  ::LoadLibraryW(L"mozavutil.dll");
-
   if (GetEffectiveContentSandboxLevel() > 7) {
     // Libraries required by Network Security Services (NSS).
     ::LoadLibraryW(L"freebl3.dll");