Bug 1517483 - Get rid of nsIScriptSecurityManager::IsSystemPrincipal r=bzbarsky

Replaced instances of callers in both C++ and JS files to query the state from the principal directly.

Differential Revision: https://phabricator.services.mozilla.com/D22532

toolkit/components/backgroundhangmonitor/ThreadStackHelper.cpp

@@ -210,12 +210,9 @@ namespace {
 bool IsChromeJSScript(JSScript* aScript) {
   // May be called from another thread or inside a signal handler.
   // We assume querying the script is safe but we must not manipulate it.
-  nsIScriptSecurityManager* const secman =
-      nsScriptSecurityManager::GetScriptSecurityManager();
-  NS_ENSURE_TRUE(secman, false);
 
   JSPrincipals* const principals = JS_GetScriptPrincipals(aScript);
-  return secman->IsSystemPrincipal(nsJSPrincipals::get(principals));
+  return nsJSPrincipals::get(principals)->IsSystemPrincipal();
 }
 
 // Get the full path after the URI scheme, if the URI matches the scheme.