update_engine: Rename "chromeos" -> "brillo" in include paths and namespaces

libchromeos is transitioning to libbrillo and chromeos namespaces
and include directory is changing to brillo.

Bug: 24872993
Change-Id: I770659a95be380a50fe3b2ba9f91d65818f40945
diff --git a/update_manager/variable.h b/update_manager/variable.h
index a568a37..98774ef 100644
--- a/update_manager/variable.h
+++ b/update_manager/variable.h
@@ -25,7 +25,7 @@
 #include <base/location.h>
 #include <base/logging.h>
 #include <base/time/time.h>
-#include <chromeos/message_loops/message_loop.h>
+#include <brillo/message_loops/message_loop.h>
 #include <gtest/gtest_prod.h>  // for FRIEND_TEST
 
 namespace chromeos_update_manager {
@@ -120,7 +120,7 @@
     // to avoid scheduling these callbacks when it is not needed, we check
     // first the list of observers.
     if (!observer_list_.empty()) {
-      chromeos::MessageLoop::current()->PostTask(
+      brillo::MessageLoop::current()->PostTask(
           FROM_HERE,
           base::Bind(&BaseVariable::OnValueChangedNotification,
                      base::Unretained(this)));