[Android] Add a configurable environment for devil/. (RELAND)

build/android/devil/android/sdk/adb_wrapper.py

Index: build/android/devil/android/sdk/adb_wrapper.py
diff --git a/build/android/devil/android/sdk/adb_wrapper.py b/build/android/devil/android/sdk/adb_wrapper.py
index 5a81c7fe503b634f583e29d40f92bd6515948bf8..184568f60cd05d29bb05ad0b7734af85f9d97bd5 100644
--- a/build/android/devil/android/sdk/adb_wrapper.py
+++ b/build/android/devil/android/sdk/adb_wrapper.py
@@ -13,12 +13,13 @@ import errno
 import logging
 import os
 import re
+import threading
 
+from devil import devil_env
 from devil.android import decorators
 from devil.android import device_errors
 from devil.utils import cmd_helper
 from devil.utils import timeout_retry
-from pylib import constants
 
 
 _DEFAULT_TIMEOUT = 30
@@ -49,6 +50,9 @@ DeviceStat = collections.namedtuple('DeviceStat',
 class AdbWrapper(object):
   """A wrapper around a local Android Debug Bridge executable."""
 
+  _adb_path = None
+  _adb_path_lock = threading.Lock()
+
   def __init__(self, device_serial):
     """Initializes the AdbWrapper.
 
@@ -59,19 +63,25 @@ class AdbWrapper(object):
       raise ValueError('A device serial must be specified')
     self._device_serial = str(device_serial)
 
-  # pylint: disable=unused-argument
+  @classmethod
+  def _GetAdbPath(cls):
+    if not cls._adb_path:
+      with cls._adb_path_lock:
+        if not cls._adb_path:
+          cls._adb_path = devil_env.config.FetchPath('adb')
+    return cls._adb_path
+
   @classmethod
   def _BuildAdbCmd(cls, args, device_serial, cpu_affinity=None):
     if cpu_affinity is not None:
       cmd = ['taskset', '-c', str(cpu_affinity)]
     else:
       cmd = []
-    cmd.append(constants.GetAdbPath())
+    cmd.append(cls._GetAdbPath())
     if device_serial is not None:
       cmd.extend(['-s', device_serial])
     cmd.extend(args)
     return cmd
-  # pylint: enable=unused-argument
 
   # pylint: disable=unused-argument
   @classmethod