[Android] Allow __NR_process_vm_readv under Seccomp.

Bug: 766245
Change-Id: Ic494f526c1b8d15483ca7e9a97d9f044f276c26d
Reviewed-on: https://chromium-review.googlesource.com/671556Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502714}

sandbox/linux/seccomp-bpf-helpers/baseline_policy_android.cc

@@ -149,6 +149,13 @@ ResultExpr BaselinePolicyAndroid::EvaluateSyscall(int sysno) const {
            .Else(Error(EPERM));
   }
 
+  // https://crbug.com/766245
+  if (sysno == __NR_process_vm_readv) {
+    const Arg<pid_t> pid(0);
+    return If(pid == policy_pid(), Allow())
+           .Else(Error(EPERM));
+  }
+
   // https://crbug.com/655299
   if (sysno == __NR_clock_getres) {
     return RestrictClockID();