Start all children in their own PID namespace.

sandbox/linux/services/credentials.cc

Index: sandbox/linux/services/credentials.cc
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index c8c679d8515e16db91e2636315f3974747b5066a..e8dd1d943cb0278b439f0efbc07d26f5416629d7 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -148,6 +148,21 @@ bool Credentials::DropAllCapabilities() {
   return Credentials::DropAllCapabilities(proc_fd.get());
 }
 
+// static
+bool Credentials::SetCapabilities(int proc_fd,
+                                  const std::vector<cap_value_t>& caps) {
+  DCHECK_LE(0, proc_fd);
+  CHECK(ThreadHelpers::IsSingleThreaded(proc_fd));
+
+  sandbox::ScopedCap cap(cap_init());
+  PCHECK(cap != nullptr);
+  cap_flag_t flags[] = {CAP_EFFECTIVE, CAP_PERMITTED};
+  for (const cap_flag_t flag : flags) {
+    PCHECK(cap_set_flag(cap.get(), flag, caps.size(), &caps[0], CAP_SET) == 0);
+  }
+  return cap_set_proc(cap.get()) == 0;
+}
+
 bool Credentials::HasAnyCapability() {
   ScopedCap current_cap(cap_get_proc());
   CHECK(current_cap);