Linux Sandbox: fix external StartSandbox API

content/common/sandbox_seccomp_bpf_linux.cc

Index: content/common/sandbox_seccomp_bpf_linux.cc
diff --git a/content/common/sandbox_seccomp_bpf_linux.cc b/content/common/sandbox_seccomp_bpf_linux.cc
index 61fdf7aa902e6209444ba0aa9669702370c91d7f..a8e1caa05f85839f86ff9c82122d864158095228 100644
--- a/content/common/sandbox_seccomp_bpf_linux.cc
+++ b/content/common/sandbox_seccomp_bpf_linux.cc
@@ -1948,7 +1948,7 @@ bool SandboxSeccompBpf::StartSandbox(const std::string& process_type) {
 bool SandboxSeccompBpf::StartSandboxWithExternalPolicy(
     playground2::BpfSandboxPolicy policy) {
 #if defined(SECCOMP_BPF_SANDBOX)
-  if (IsSeccompBpfDesired()) {
+  if (IsSeccompBpfDesired() && SupportsSandbox()) {
     CHECK(policy);
     StartSandboxWithPolicy(policy, NULL);
     return true;