[Android] Support generic parallel execution across devices.

build/android/pylib/utils/reraiser_thread.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.
 
 """Thread and ThreadGroup that reraise exceptions on the main thread."""
 # pylint: disable=W0212
 
 import logging
 import sys
 import threading
@@ skipping 38 matching lines @@
     """
     super(ReraiserThread, self).__init__(name=name)
     if not args:
       args = []
     if not kwargs:
       kwargs = {}
     self.daemon = True
     self._func = func
     self._args = args
     self._kwargs = kwargs
+    self._ret = None
     self._exc_info = None
 
   def ReraiseIfException(self):
     """Reraise exception if an exception was raised in the thread."""
     if self._exc_info:
       raise self._exc_info[0], self._exc_info[1], self._exc_info[2]
 
+  def GetReturnValue(self):
+    """Reraise exception if present, otherwise get the return value."""
+    self.ReraiseIfException()
+    return self._ret
+
   #override
   def run(self):
     """Overrides Thread.run() to add support for reraising exceptions."""
     try:
-      self._func(*self._args, **self._kwargs)
+      self._ret = self._func(*self._args, **self._kwargs)
     except:
       self._exc_info = sys.exc_info()
       raise
 
 
 class ReraiserThreadGroup(object):
   """A group of ReraiserThread objects."""
 
   def __init__(self, threads=None):
     """Initialize thread group.
@@ skipping 50 matching lines @@
 
     Args:
       watcher: Watchdog object providing timeout, by default waits forever.
     """
     try:
       self._JoinAll(watcher)
     except TimeoutError:
       for thread in (t for t in self._threads if t.isAlive()):
         LogThreadStack(thread)
       raise
+
+  def GetAllReturnValues(self, watcher=watchdog_timer.WatchdogTimer(None)):
+    """Get all return values, joining all threads if necessary.
+
+    Args:
+      watcher: same as in |JoinAll|. Only used if threads are alive.
+    """
+    if any([t.isAlive() for t in self._threads]):
+      self.JoinAll(watcher)
+    return [t.GetReturnValue() for t in self._threads]
+