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.h b/filesystem_verifier_action.h
index 731790a..e6c1908 100644
--- a/filesystem_verifier_action.h
+++ b/filesystem_verifier_action.h
@@ -44,7 +44,7 @@
   // Used for testing. Return true if Cleanup() has not yet been called due
   // to a callback upon the completion or cancellation of the verifier action.
   // A test should wait until IsCleanupPending() returns false before
-  // terminating the glib main loop.
+  // terminating the main loop.
   bool IsCleanupPending() const;
 
   // Debugging/logging