Use O_NONBLOCK when opening audio pipe on linux.

By default open() blocks when opening a fifo until the writer also
opens the fifo. In the past AudioPipeReader was using O_NONBLOCK
when opening the pipe for reading, but that was changed in r277315,
and may result in host hanging if pulseaudio doesn't open the pipe
for some reason. Fixed AudioPipeReader to always pass O_NONBLOCK
to open().

BUG=420090
R=lambroslambrou@chromium.org

Review URL: https://codereview.chromium.org/820123002

Cr-Commit-Position: refs/heads/master@{#309592}

remoting/host/linux/audio_pipe_reader.cc

@@ -107,10 +107,8 @@ void AudioPipeReader::OnDirectoryChanged(const base::FilePath& path,
 void AudioPipeReader::TryOpenPipe() {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
-  base::File new_pipe;
-  new_pipe.Initialize(
-      pipe_path_,
-      base::File::FLAG_OPEN | base::File::FLAG_READ | base::File::FLAG_ASYNC);
+  base::File new_pipe(
+      HANDLE_EINTR(open(pipe_path_.value().c_str(), O_RDONLY | O_NONBLOCK)));
 
   // If both |pipe_| and |new_pipe| are valid then compare inodes for the two
   // file descriptors. Don't need to do anything if inode hasn't changed.
@@ -130,13 +128,6 @@ void AudioPipeReader::TryOpenPipe() {
   pipe_ = new_pipe.Pass();
 
   if (pipe_.IsValid()) {
-    // Set O_NONBLOCK flag.
-    if (HANDLE_EINTR(fcntl(pipe_.GetPlatformFile(), F_SETFL, O_NONBLOCK)) < 0) {
-      PLOG(ERROR) << "fcntl";
-      pipe_.Close();
-      return;
-    }
-
     // Set buffer size for the pipe.
     if (HANDLE_EINTR(fcntl(
             pipe_.GetPlatformFile(), F_SETPIPE_SZ, kPipeBufferSizeBytes)) < 0) {