c/b/ui: allow circular includes from c/b

Tested on Linux with the following command line:
$ gn gen out-gn/Release --args='is_debug=false is_component_build=false symbol_level=1'
$ gn check out-gn/Release //chrome/browser/ui:ui

BUG=367595,376000
TEST=see above
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Review URL: https://codereview.chromium.org/1730643002

Cr-Commit-Position: refs/heads/master@{#378803}
4 files changed