Add chrome-bot ps output to system statistics log.

Currently the system statistics contain top output which truncates
executable names.  Adding ps output will give full executable names
and invocation arguments.

Bug: 1100402
Change-Id: I5357fea58e0dbf04dacdc6b6caabf5b2d79ea856
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2335649Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: Stephen Roe <steveroe@google.com>
Cr-Commit-Position: refs/heads/master@{#794628}

build/fuchsia/emu_target.py

@@ -129,8 +129,13 @@ class EmuTarget(target.Target):
 
 # TODO(crbug.com/1100402): Delete when no longer needed for debug info.
 def _LogSystemStatistics(log_file_name):
+  statistics_log = runner_logs.FileStreamFor(log_file_name)
   # Log the cpu load and process information.
   subprocess.call(['top', '-b', '-n', '1'],
                   stdin=open(os.devnull),
-                  stdout=runner_logs.FileStreamFor(log_file_name),
+                  stdout=statistics_log,
+                  stderr=subprocess.STDOUT)
+  subprocess.call(['ps', '-ax'],
+                  stdin=open(os.devnull),
+                  stdout=statistics_log,
                   stderr=subprocess.STDOUT)