Work on getting things built with -Wimplicit-fallthrough. This CL was uploaded by git cl split.

Bug: 177475
R=palmer@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.android:android_arm64_dbg_recipe;master.tryserver.chromium.android:android_compile_mips_dbg;master.tryserver.chromium.android:android_compile_x64_dbg;master.tryserver.chromium.android:android_compile_x86_dbg
Change-Id: I361d9b71990cbb9870760709748d1928055b779c
Reviewed-on: https://chromium-review.googlesource.com/889787
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532129}

sandbox/linux/integration_tests/bpf_dsl_seccomp_unittest.cc

@@ -774,6 +774,7 @@ ResultExpr SimpleCondTestPolicy::EvaluateSyscall(int sysno) const {
 #if defined(__NR_open)
     case __NR_open:
       flags_argument_position = 1;
+      FALLTHROUGH;
 #endif
     case __NR_openat: {  // open can be a wrapper for openat(2).
       if (sysno == __NR_openat)