buffet: Add ExportedObjectManager delegate

This makes it easy to export an object manager.  We'll use this very
soon to implement the ObjectManager interface on the root Buffet
object.

BUG=chromium:359190
TEST=Unittests

Change-Id: I19d2da33b81557431c5787937c49a18e7d7bacb2
Reviewed-on: https://chromium-review.googlesource.com/196387
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
Tested-by: Christopher Wiley <wiley@chromium.org>
diff --git a/buffet/buffet.gyp b/buffet/buffet.gyp
index c4c5a1b..b94677c 100644
--- a/buffet/buffet.gyp
+++ b/buffet/buffet.gyp
@@ -32,6 +32,7 @@
         'dbus_manager.cc',
         'dbus_utils.cc',
         'device_registration_info.cc',
+        'exported_object_manager.cc',
         'exported_property_set.cc',
         'http_request.cc',
         'http_connection_curl.cc',
@@ -77,6 +78,7 @@
         'buffet_testrunner.cc',
         'data_encoding_unittest.cc',
         'device_registration_info_unittest.cc',
+        'exported_object_manager_unittest.cc',
         'exported_property_set_unittest.cc',
         'http_connection_fake.cc',
         'http_transport_fake.cc',