Bug 1416016 - Add ../config to the sandbox whitelist for older Mesa. r=jld

MozReview-Commit-ID: KahivmVJR1l

--HG--
extra : rebase_source : 7d77f0ee77813a1214cfa5bc618b57c3208443c3

security/sandbox/linux/broker/SandboxBrokerPolicyFactory.cpp

@@ -82,7 +82,9 @@ AddMesaSysfsPaths(SandboxBroker::Policy* aPolicy)
             UniqueFreePtr<char[]> realSysPath(realpath(sysPath.get(), nullptr));
             if (realSysPath) {
               nsPrintfCString ueventPath("%s/uevent", realSysPath.get());
+              nsPrintfCString configPath("%s/config", realSysPath.get());
               aPolicy->AddPath(rdonly, ueventPath.get());
+              aPolicy->AddPath(rdonly, configPath.get());
             }
           }
         }