In the context of a CL [1] moving some extension IDs out of //chrome, some oddities came up:

* extensions::kWebStoreAppId is the only extension ID defined in extensions/common/constants.h not in the extension_misc namespace

* file_manager::kFileManagerAppId is redundant with extension_misc::kFilesManagerAppId (chrome/browser/chromeos already depends on //extensions so there's no need for it to define its own version of this constant)

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1189168