libchromeos: Clean up/moved file into sub-directories

Moved related files in libchromeos into sub-directories
to make it easier to navigate code.

BUG=None
TEST=FEATURES=test emerge-link libchromeos buffet peerd
CQ-DEPEND=CL:214763

Change-Id: I50d690f19f09a8f4d0da1154e63f58c76c415a55
Reviewed-on: https://chromium-review.googlesource.com/214499
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/commands/command_dictionary.cc b/buffet/commands/command_dictionary.cc
index 54753ad..51ffb3d 100644
--- a/buffet/commands/command_dictionary.cc
+++ b/buffet/commands/command_dictionary.cc
@@ -5,7 +5,7 @@
 #include "buffet/commands/command_dictionary.h"
 
 #include <base/values.h>
-#include <chromeos/string_utils.h>
+#include <chromeos/strings/string_utils.h>
 
 #include "buffet/commands/command_definition.h"
 #include "buffet/commands/schema_constants.h"