buffet: Remove 'chromeos' namespace and move everything to buffet NS

As discussed, moved all the classes out of chromeos namespace into
'buffet.

Also fixed a number of cpplint's warnings.

BUG=None
TEST=Everything still compiles and unit tests succeed.

Change-Id: Ide864acb2504627404966727f66d353af60e531d
Reviewed-on: https://chromium-review.googlesource.com/198971
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/device_registration_info_unittest.cc b/buffet/device_registration_info_unittest.cc
index 5456ca0..5108e35 100644
--- a/buffet/device_registration_info_unittest.cc
+++ b/buffet/device_registration_info_unittest.cc
@@ -15,8 +15,7 @@
 #include "buffet/storage_impls.h"
 
 using namespace buffet;          // NOLINT(build/namespaces)
-using namespace chromeos;        // NOLINT(build/namespaces)
-using namespace chromeos::http;  // NOLINT(build/namespaces)
+using namespace buffet::http;    // NOLINT(build/namespaces)
 
 namespace {