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_unittest.cc b/update_manager/variable_unittest.cc
index 0622db0..13cceb1 100644
--- a/update_manager/variable_unittest.cc
+++ b/update_manager/variable_unittest.cc
@@ -18,14 +18,14 @@
 
 #include <vector>
 
-#include <chromeos/message_loops/fake_message_loop.h>
-#include <chromeos/message_loops/message_loop.h>
-#include <chromeos/message_loops/message_loop_utils.h>
+#include <brillo/message_loops/fake_message_loop.h>
+#include <brillo/message_loops/message_loop.h>
+#include <brillo/message_loops/message_loop_utils.h>
 #include <gtest/gtest.h>
 
 using base::TimeDelta;
-using chromeos::MessageLoop;
-using chromeos::MessageLoopRunMaxIterations;
+using brillo::MessageLoop;
+using brillo::MessageLoopRunMaxIterations;
 using std::string;
 using std::vector;
 
@@ -57,7 +57,7 @@
     loop_.SetAsCurrent();
   }
 
-  chromeos::FakeMessageLoop loop_{nullptr};
+  brillo::FakeMessageLoop loop_{nullptr};
 };
 
 TEST_F(UmBaseVariableTest, GetNameTest) {