I think you started this work already 

The following revision refers to this bug:
  https://chromium.googlesource.com/external/github.com/luci/luci-go.git/+/e0e9f21852f8e48d79169e16d7000731422cec8d

commit e0e9f21852f8e48d79169e16d7000731422cec8d
Author: hinoka <hinoka@google.com>
Date: Mon Mar 20 19:24:08 2017

Milo Refactor: Remove theme support and bootstrap theme

This CL:
* Removes the bootstrap theme (It hasn't been maintained for a while)(
* Removes theming support
* Renames settings to common
* Renames settings/settings.go to middleware.go
* Moves the expectation and template folders so they're not nested by theme name.
* Remove the ThemedHandler type and replace it with normal handlers that matches the rest of luci-go.
* Remove the TestData type and replace them with functions.

BUG= 698846 

Review-Url: https://codereview.chromium.org/2748073006

[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/api/proto/pb.discovery.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/build.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/build_test.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/builder.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/html.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/html_data.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/master.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbot/pubsub_test.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbucket/builder.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbucket/builder_test.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/buildbucket/html.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/acl.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/acl_test.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/config.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/config_test.go
[add] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/error.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/funcs.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/funcs_test.go
[add] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/middleware.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/testBundle.go
[add] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/common/utils.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/console/console.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/console/html.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/console/html_data.go
[add] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/config.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-buildbot.TestableBuild-Debug_page-_CrWinGoma_30608.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-buildbot.TestableBuild-Debug_page-_win_chromium_rel_ng_246309.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-buildbot.TestableBuilder-Basic_Test_no_builds.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-buildbot.TestableBuilder-Basic_Test_with_builds.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-frontend.testableFrontpage-Basic_frontpage.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-settings.TestableSettings-Settings.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-Basic_successful_build.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-canceled.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-exception.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-expired.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-hang.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-link.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-nested.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-patch-failure.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-pending-logdog.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-pending.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-running-logdog-no-annotation-stream.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-running-logdog.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-running.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-timeout.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableBuild-build-unicode.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/bootstrap-swarming.TestableLog-Basic_log.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/buildbot-settings.TestableSettings-Settings.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/expectations/buildbot-swarming.TestableBuild-build-hang.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/buildbot.build-Debug_page-_CrWinGoma_30608.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/buildbot.build-Debug_page-_win_chromium_rel_ng_246309.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/buildbot.builder-Basic_Test_no_builds.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/buildbot.builder-Basic_Test_with_builds.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/frontpage-Basic_frontpage.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-Basic_successful_build.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-canceled.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-exception.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-expired.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-link.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-nested.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-patch-failure.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-pending-logdog.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-pending.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-running-logdog-no-annotation-stream.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-running-logdog.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-running.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-timeout.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.build-build-unicode.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/expectations/swarming.log-Basic_log.html
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/frontpage.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/main.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/main_test.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/includes/bootstrap.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/build.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/builder.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/error.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/frontpage.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/log.html
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/frontend/templates/bootstrap/pages/settings.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/includes/base.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/build.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/builder.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/configs.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/console.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/error.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/frontpage.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/log.html
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/frontend/templates/pages/settings.html
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/logdog/build.go
[rename] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/logdog/html.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/settings/html.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/settings/html_data.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/settings/settings.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/appengine/settings/themes.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/swarming/html.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/appengine/swarming/html_data.go
[modify] https://crrev.com/e0e9f21852f8e48d79169e16d7000731422cec8d/milo/common/config/project.pb.go
[delete] https://crrev.com/25242b2bc72df05066ffbfcd54ef39edcaafbf04/milo/common/miloerror/error.go