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/libcurl_http_fetcher.cc b/libcurl_http_fetcher.cc
index 5b6c605..8a3fd3b 100644
--- a/libcurl_http_fetcher.cc
+++ b/libcurl_http_fetcher.cc
@@ -30,7 +30,7 @@
 #include "update_engine/hardware_interface.h"
 
 using base::TimeDelta;
-using chromeos::MessageLoop;
+using brillo::MessageLoop;
 using std::max;
 using std::string;