Update from chromium https://crrev.com/302282

build/android/pylib/utils/watchdog_timer.py

 # Copyright 2013 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.
 
 """WatchdogTimer timeout objects."""
 
 import time
 
 
 class WatchdogTimer(object):
   """A resetable timeout-based watchdog.
 
   This object is threadsafe.
   """
 
   def __init__(self, timeout):
     """Initializes the watchdog.
 
     Args:
       timeout: The timeout in seconds. If timeout is None it will never timeout.
     """
     self._start_time = time.time()
     self._timeout = timeout
 
   def Reset(self):
     """Resets the timeout countdown."""
     self._start_time = time.time()
 
+  def GetElapsed(self):
+    """Returns the elapsed time of the watchdog."""
+    return time.time() - self._start_time
+
+  def GetRemaining(self):
+    """Returns the remaining time of the watchdog."""
+    if self._timeout:
+      return self._timeout - self.GetElapsed()
+    else:
+      return None
+
   def IsTimedOut(self):
     """Whether the watchdog has timed out.
 
     Returns:
       True if the watchdog has timed out, False otherwise.
     """
-    if self._timeout is None:
-      return False
-    return time.time() - self._start_time > self._timeout
+    remaining = self.GetRemaining()
+    return remaining is not None and remaining < 0