Update web-platform-tests docs

docs/linux_sandboxing.md

 # Linux Sandboxing
 
 Chromium uses a multiprocess model, which allows to give different privileges
 and restrictions to different parts of the browser. For instance, we want
 renderers to run with a limited set of privileges since they process untrusted
 input and are likely to be compromised. Renderers will use an IPC mechanism to
 request access to resource from a more privileged (browser process).
 You can find more about this general design
 [here](https://dev.chromium.org/developers/design-documents/sandbox).
 
@@ skipping 23 matching lines @@
 using `open()` on `/proc` entries.
 
 Our layer-1 guarantees the integrity of processes running under different
 `seccomp-bpf` policies. In addition, it allows restricting access to the
 network, something that is difficult to perform at the layer-2.
 
 ## Sandbox types summary
 
 | **Name** | **Layer and process** | **Linux flavors where available** | **State** |
 |:---------|:----------------------|:----------------------------------|:----------|
-| [Setuid sandbox](#The_setuid_sandbox.md) | Layer-1 in Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient), some utility processes) | Linux distributions and Chrome OS | Enabled by default (old kernels) and maintained |
-| [User namespaces sandbox](#User_namespaces_sandbox.md) | Modern alternative to the setuid sandbox. Layer-1 in Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient), some utility processes) | Linux distributions and Chrome OS (kernel >= 3.8) | Enabled by default (modern kernels) and actively developed |
-| [Seccomp-BPF](#The_seccomp-bpf_sandbox.md) | Layer-2 in some Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient)), Layer-1 + Layer-2 in GPU process | Linux kernel >= 3.5, Chrome OS and Ubuntu | Enabled by default and actively developed |
-| [Seccomp-legacy](#The_seccomp_sandbox.md) | Layer-2 in renderers  | All                               | [Deprecated](https://src.chromium.org/viewvc/chrome?revision=197301&view=revision)  |
-| [SELinux](#SELinux.md) | Layer-1 in Zygote processes (renderers, PPAPI) | SELinux distributions             | [Deprecated](https://src.chromium.org/viewvc/chrome?revision=200838&view=revision) |
+| [Setuid sandbox](#The-setuid-sandbox) | Layer-1 in Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient), some utility processes) | Linux distributions and Chrome OS | Enabled by default (old kernels) and maintained |
+| [User namespaces sandbox](#User-namespaces-sandbox) | Modern alternative to the setuid sandbox. Layer-1 in Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient), some utility processes) | Linux distributions and Chrome OS (kernel >= 3.8) | Enabled by default (modern kernels) and actively developed |
+| [Seccomp-BPF](#The-sandbox-1) | Layer-2 in some Zygote processes (renderers, PPAPI, [NaCl](https://www.chromium.org/nativeclient)), Layer-1 + Layer-2 in GPU process | Linux kernel >= 3.5, Chrome OS and Ubuntu | Enabled by default and actively developed |
+| [Seccomp-legacy](#The-sandbox-2) | Layer-2 in renderers  | All                               | [Deprecated](https://src.chromium.org/viewvc/chrome?revision=197301&view=revision)  |
+| [SELinux](#SELinux) | Layer-1 in Zygote processes (renderers, PPAPI) | SELinux distributions             | [Deprecated](https://src.chromium.org/viewvc/chrome?revision=200838&view=revision) |
 | AppArmor | Outer layer-1 in Zygote processes (renderers, PPAPI) | Not used                          | Deprecated |
 
 ## The setuid sandbox
 
 Also called SUID sandbox, our main layer-1 sandbox.
 
 A SUID binary that will create a new network and PID namespace, as well as
 `chroot()` the process to an empty directory on request.
 
 To disable it, use `--disable-setuid-sandbox`. (Do not remove the binary or
@@ skipping 83 matching lines @@
 
 *   [this page](linux_suid_sandbox_development.md) for the `setuid` sandbox
 *   [this page](https://www.chromium.org/for-testers/bug-reporting-guidelines/hanging-tabs)
     for triggering crashes
 *   [this page for debugging tricks](linux_debugging.md)
 
 ## See also
 
 *   [LinuxSandboxIPC](linux_sandbox_ipc.md)
 *   [How Chromium's Linux sandbox affects Native Client](https://chromium.googlesource.com/native_client/src/native_client.git/+/master/docs/linux_outer_sandbox.md)