Create pulseaudio upstart job, and add default client configurations + startup volume.

src/platform/init/pulseaudio.conf

+# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+description   "Run pulseaudio when the system starts"
+author        "chromium-os-dev@googlegroups.com"
+
+start on started syslog
+stop on starting halt
+respawn
+
+env USERNAME=chronos
+env XAUTHORITY=/home/chronos/.Xauthority
+env DISPLAY=:0.0
+# TODO(ajwong): pulseaudio wants CAP_NICE.  Readd --use-capabilities after
+# resolving that dependency.
+env MINIJAIL_FLAGS=""
+env PULSEAUDIO_FIRST_RUN=/tmp/pulseaudio-first-run
+env PULSE_STATE_PATH=/home/chronos/.pulse
+env PULSE_RUNTIME_PATH=/var/run/pulse
+env USER_ID=1000
+
+pre-start script
+  # Signal whether or not we need to do initial configuration of pulseaudio.
+  if [ -d ${PULSE_STATE_PATH} ]; then
+    rm -f "${PULSEAUDIO_FIRST_RUN}"
+  else
+    # Try to clean out any bad cruft at this directory, just incase.
+    rm -rf "${PULSE_STATE_PATH}"
+    touch "${PULSEAUDIO_FIRST_RUN}"
+  fi
+end script
+
+script
+  # Create pulseaudio runtime directory for pulseaudio's pidfile and socket.
+  mkdir -p "${PULSE_RUNTIME_PATH}"
+  chown -R chronos:chronos "${PULSE_RUNTIME_PATH}"
+
+  if [ -f "${PULSEAUDIO_FIRST_RUN}" ] ; then
+    # Clean up the first-run signal file.
+    rm -f "${PULSEAUDIO_FIRST_RUN}"
+    exec /sbin/minijail ${MINIJAIL_FLAGS} --uid=${USER_ID} -- \
+      /usr/bin/pulseaudio -F /etc/pulse/firstrun.pa
+  else
+    exec /sbin/minijail ${MINIJAIL_FLAGS} --uid=${USER_ID} -- \
+      /usr/bin/pulseaudio
+  fi
+end script