Add option to specify ADB binary in test runner.

third_party/android_testrunner/adb_interface.py

Index: third_party/android_testrunner/adb_interface.py
diff --git a/third_party/android_testrunner/adb_interface.py b/third_party/android_testrunner/adb_interface.py
index 93e19632a84b08da4269e2f8b965d4c392b42c4d..179aca95d9d0c840bab450715d9a606c46c1208f 100644
--- a/third_party/android_testrunner/adb_interface.py
+++ b/third_party/android_testrunner/adb_interface.py
@@ -37,8 +37,20 @@ class AdbInterface:
   # argument to pass to adb, to direct command to specific device
   _target_arg = ""
 
+  # argument used to specify adb binary. Defaults to adb in the
+  # environment path.
+  _adb_path = 'adb'
+
   DEVICE_TRACE_DIR = "/data/test_results/"
 
+  def SetAdbPath(self, adb_path):
+    """Set the path to the adb binary.
+
+    Args:
+      adb_path: absolute path to the adb binary that should be used.
+    """
+    self._adb_path = adb_path
+
   def SetEmulatorTarget(self):
     """Direct all future commands to the only running emulator."""
     self._target_arg = "-e"
@@ -66,7 +78,7 @@ class AdbInterface:
     Raises:
       WaitForResponseTimedOutError if device does not respond to command within time
     """
-    adb_cmd = "adb %s %s" % (self._target_arg, command_string)
+    adb_cmd = "%s %s %s" % (self._adb_path, self._target_arg, command_string)
     logger.SilentLog("about to run %s" % adb_cmd)
     return run_command.RunCommand(adb_cmd, timeout_time=timeout_time,
                                   retry_count=retry_count)