update_engine: Remove all references to glib.

The message loop in production code switched from
chromeos::GlibMessageLoop to chromeos::BaseMessageLoop used in
chromeos::Dameon. This patch moves all the unittests also to use
chromeos::BaseMessageLoop or chromeos::FakeMessageLoop when I/O is not
required.

This patch removes all (now unused) references to glib.

BUG=chromium:499886
TEST=`grep glib[^c] . -R` return no results. Also, unittests work.

Change-Id: Iddfb17def501829d932ed1f70faad3e00268898e
Reviewed-on: https://chromium-review.googlesource.com/292157
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Trybot-Ready: Alex Deymo <deymo@chromium.org>
diff --git a/filesystem_verifier_action_unittest.cc b/filesystem_verifier_action_unittest.cc
index 66f8571..9ddeb29 100644
--- a/filesystem_verifier_action_unittest.cc
+++ b/filesystem_verifier_action_unittest.cc
@@ -14,7 +14,7 @@
 #include <base/posix/eintr_wrapper.h>
 #include <base/strings/string_util.h>
 #include <base/strings/stringprintf.h>
-#include <chromeos/message_loops/glib_message_loop.h>
+#include <chromeos/message_loops/fake_message_loop.h>
 #include <chromeos/message_loops/message_loop_utils.h>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
@@ -47,7 +47,7 @@
               bool hash_fail,
               PartitionType partition_type);
 
-  chromeos::GlibMessageLoop loop_;
+  chromeos::FakeMessageLoop loop_{nullptr};
   FakeSystemState fake_system_state_;
 };