[autotest] Added Host for emulated adb devices.

Minor changes to factory and utilities. Added EmulatorManager class to
handle the grunt work and EmulatedADBHost to interface with emulated
devices.

CQ-DEPEND=360512
BUG=None
TEST=Ran dummy tests on emulator with install from go/ab. Also verified
on dragonboard.

Change-Id: I3058e886deeb256e9187c4313d34f807b34eb58d
Reviewed-on: https://chromium-review.googlesource.com/360220
Commit-Ready: Justin Giorgi <jgiorgi@google.com>
Tested-by: Justin Giorgi <jgiorgi@google.com>
Reviewed-by: Simran Basi <sbasi@chromium.org>
diff --git a/server/hosts/factory.py b/server/hosts/factory.py
index 1829d65..3619717 100644
--- a/server/hosts/factory.py
+++ b/server/hosts/factory.py
@@ -10,7 +10,7 @@
 from autotest_lib.server.cros.dynamic_suite import constants
 from autotest_lib.server.hosts import cros_host, ssh_host
 from autotest_lib.server.hosts import moblab_host, sonic_host
-from autotest_lib.server.hosts import adb_host, testbed
+from autotest_lib.server.hosts import adb_host, emulated_adb_host, testbed
 
 
 CONFIG = global_config.global_config
@@ -34,7 +34,8 @@
               adb_host.ADBHost,]
 OS_HOST_DICT = {'cros' : cros_host.CrosHost,
                 'android': adb_host.ADBHost,
-                'brillo': adb_host.ADBHost}
+                'brillo': adb_host.ADBHost,
+                'emulated_brillo': emulated_adb_host.EmulatedADBHost}
 
 
 def _get_host_arguments(machine):