Make VR latency results compatible with perf dashboard, refactor into classes

chrome/test/vr/perf/latency/robot_arm.py

+# Copyright 2017 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.
+
+import serial
+import time
+
+
+class RobotArm():
+  """Handles the serial communication with the servos/arm used for movement."""
+  def __init__(self, device_name, num_tries=5, baud=115200, timeout=3.0):
+    self._connection = None
+    connected = False
+    for _ in xrange(num_tries):
+      try:
+        self._connection = serial.Serial('/dev/' + device_name,
+                                         baud,
+                                         timeout=timeout)
+      except serial.SerialException as e:
+        pass
+      if self._connection and 'Enter parameters' in self._connection.read(1024):
+        connected = True
+        break
+    if not connected:
+      raise serial.SerialException('Failed to connect to the robot arm.')
+
+  def ResetPosition(self):
+    if not self._connection:
+      return
+    # If the servo stopped very close to the desired position, it can just
+    # vibrate instead of moving, so move away before going to the reset
+    # position
+    self._connection.write('5 300 0 5\n')
+    time.sleep(0.5)
+    self._connection.write('5 250 0 5\n')
+    time.sleep(0.5)
+
+  def StartMotophoMovement(self):
+    if not self._connection:
+      return
+    self._connection.write('9\n')
+
+  def StopAllMovement(self):
+    if not self._connection:
+      return
+    self._connection.write('0\n')