video_HangoutHardwarePerf - Add the test to monitor the performance

Add the video_HangoutHardwarePerf test, in which we start hardware
encoders and decoders simutaneously in a hangout-like scenarios and
the performance.

BUG=chromium:350255
TEST=Run the test on peach-pit

Change-Id: I807c9c326d100cf23e7c48c52ada7999b29dcd28
Reviewed-on: https://chromium-review.googlesource.com/235692
Reviewed-by: Owen Lin <owenlin@chromium.org>
Commit-Queue: Owen Lin <owenlin@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
Reviewed-by: Kuang-che Wu <kcwu@chromium.org>
diff --git a/client/cros/audio/cmd_utils.py b/client/cros/audio/cmd_utils.py
index d6423a1..ee43e2d 100644
--- a/client/cros/audio/cmd_utils.py
+++ b/client/cros/audio/cmd_utils.py
@@ -161,7 +161,7 @@
     return out
 
 
-def popen(args, stdin=None, stdout=TEE_TO_LOGS, stderr=TEE_TO_LOGS):
+def popen(args, stdin=None, stdout=TEE_TO_LOGS, stderr=TEE_TO_LOGS, env=None):
     '''Returns a Popen object just as subprocess.Popen does but with the
     executed command stored in Popen.command.
     '''
@@ -178,7 +178,8 @@
 
     # The lock is required for http://crbug.com/323843.
     with _popen_lock:
-        ps = subprocess.Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
+        ps = subprocess.Popen(args, stdin=stdin, stdout=stdout, stderr=stderr,
+            env=env)
     logging.info('%spid is %d', prefix, ps.pid)
     ps.command_id = command_id
     ps.command = command