[NaCl SDK] nacl_io: Add flow control the JavaScript pipes.

native_client_sdk/src/libraries/nacl_io/devfs/tty_node.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "nacl_io/devfs/tty_node.h"
 
 #include <assert.h>
 #include <errno.h>
 #include <signal.h>
 #include <stdio.h>
@@ skipping 92 matching lines @@
 
 Error TtyNode::Read(const HandleAttr& attr,
                     void* buf,
                     size_t count,
                     int* out_bytes) {
   EventListenerLock wait(GetEventEmitter());
   *out_bytes = 0;
 
   // If interrupted, return
   Error err = wait.WaitOnEvent(POLLIN, -1);
+  if (err == ETIMEDOUT)
+    err = EWOULDBLOCK;
   if (err != 0)
     return err;
 
   size_t bytes_to_copy = std::min(count, input_buffer_.size());
   if (IS_ICANON) {
     // Only read up to (and including) the first newline
     std::deque<char>::iterator nl =
         std::find(input_buffer_.begin(), input_buffer_.end(), '\n');
 
     if (nl != input_buffer_.end()) {
@@ skipping 165 matching lines @@
 }
 
 Error TtyNode::Tcsetattr(int optional_actions,
                          const struct termios* termios_p) {
   AUTO_LOCK(node_lock_);
   termios_ = *termios_p;
   return 0;
 }
 
 }  // namespace nacl_io