Bug 1362537 - Re-disallow accept4 in Linux content processes. r=gcp

MozReview-Commit-ID: Gml8lR1Heu1

--HG--
extra : rebase_source : 6b466f887bd1802277a506295a9c6cc575196385

security/sandbox/linux/SandboxFilter.cpp

@@ -557,7 +557,6 @@ public:
     case SYS_SEND:
     case SYS_SOCKET: // DANGEROUS
     case SYS_CONNECT: // DANGEROUS
-    case SYS_ACCEPT4: // Used by a11y; see bug 1361238
     case SYS_GETSOCKOPT:
     case SYS_SETSOCKOPT:
     case SYS_GETSOCKNAME: