Bug 1522830: Part 1 - Init legacy blocklist using gBlocklistInitFlags; r=mhowell

When we initialize the legacy blocklisting code, we should carry forward any
flags that were set by the launcher process and/or sandbox launcher.

Differential Revision: https://phabricator.services.mozilla.com/D53672

--HG--
extra : moz-landing-system : lando

browser/app/nsBrowserApp.cpp

@@ -284,7 +284,8 @@ int main(int argc, char* argv[], char* envp[]) {
   // main
   if (argc > 1 && IsArg(argv[1], "contentproc")) {
 #  ifdef HAS_DLL_BLOCKLIST
-    DllBlocklist_Initialize(eDllBlocklistInitFlagIsChildProcess);
+    DllBlocklist_Initialize(gBlocklistInitFlags |
+                            eDllBlocklistInitFlagIsChildProcess);
 #  endif
 #  if defined(XP_WIN) && defined(MOZ_SANDBOX)
     // We need to initialize the sandbox TargetServices before InitXPCOMGlue