libchromeos: Move mime_utils from Buffet to libchromeos

BUG=chromium:405714
TEST=USE=buffet ./build_packages

Change-Id: I4e0bf9600aedda9a9ac913a1234ab1b20da72777
Reviewed-on: https://chromium-review.googlesource.com/213364
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/device_registration_info_unittest.cc b/buffet/device_registration_info_unittest.cc
index f883802..268e56e 100644
--- a/buffet/device_registration_info_unittest.cc
+++ b/buffet/device_registration_info_unittest.cc
@@ -5,6 +5,7 @@
 #include <base/json/json_reader.h>
 #include <base/values.h>
 #include <chromeos/bind_lambda.h>
+#include <chromeos/mime_utils.h>
 #include <gtest/gtest.h>
 
 #include "buffet/commands/command_manager.h"
@@ -13,7 +14,6 @@
 #include "buffet/device_registration_storage_keys.h"
 #include "buffet/http_request.h"
 #include "buffet/http_transport_fake.h"
-#include "buffet/mime_utils.h"
 #include "buffet/storage_impls.h"
 
 using namespace buffet;          // NOLINT(build/namespaces)