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/file_writer_unittest.cc b/file_writer_unittest.cc
index e366419..731b6f0 100644
--- a/file_writer_unittest.cc
+++ b/file_writer_unittest.cc
@@ -24,7 +24,7 @@
 #include <vector>
 
 #include <gtest/gtest.h>
-#include <chromeos/secure_blob.h>
+#include <brillo/secure_blob.h>
 
 #include "update_engine/test_utils.h"
 #include "update_engine/utils.h"
@@ -47,7 +47,7 @@
                                 O_CREAT | O_LARGEFILE | O_TRUNC | O_WRONLY,
                                 0644));
   EXPECT_TRUE(file_writer.Write("test", 4));
-  chromeos::Blob actual_data;
+  brillo::Blob actual_data;
   EXPECT_TRUE(utils::ReadFile(path, &actual_data));
 
   EXPECT_FALSE(memcmp("test", actual_data.data(), actual_data.size()));