allow fiddles to use the futex system call; fixes fonts finally

experimental/webtry/main.cpp

 #include <sys/time.h>
 #include <sys/resource.h>
 
 #include "SkCanvas.h"
 #include "SkCommandLineFlags.h"
 #include "SkData.h"
 #include "SkForceLinking.h"
 #include "SkGraphics.h"
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
@@ skipping 20 matching lines @@
         /* List allowed syscalls. */
         ALLOW_SYSCALL(exit_group),
         ALLOW_SYSCALL(exit),
         ALLOW_SYSCALL(fstat),
         ALLOW_SYSCALL(read),
         ALLOW_SYSCALL(write),
         ALLOW_SYSCALL(close),
         ALLOW_SYSCALL(mmap),
         ALLOW_SYSCALL(munmap),
         ALLOW_SYSCALL(brk),
+        ALLOW_SYSCALL(futex),
         KILL_PROCESS,
     };
     struct sock_fprog prog = {
         SK_ARRAY_COUNT(filter),
         filter,
     };
 
     // Lock down the app so that it can't get new privs, such as setuid.
     // Calling this is a requirement for an unpriviledged process to use mode
     // 2 seccomp filters, ala SECCOMP_MODE_FILTER, otherwise we'd have to be
@@ skipping 71 matching lines @@
 
     // Write out the image as a PNG.
     SkAutoTUnref<SkImage> image(surface->newImageSnapshot());
     SkAutoTUnref<SkData> data(image->encode(SkImageEncoder::kPNG_Type, 100));
     if (NULL == data.get()) {
         printf("Failed to encode\n");
         exit(1);
     }
     stream.write(data->data(), data->size());
 }