Milo Refactor: Remove theme support

milo/appengine/settings/testable_handler.go

-// Copyright 2016 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-// Data Structures used for defining test data for use with testing each theme.
-
-package settings
-
-import (
-        "github.com/luci/luci-go/server/templates"
-)
-
-// TestableHandler pairs up a handler with a list of test data.
-type TestableHandler interface {
-        // ThemedHandler represents the Hanler that this TestableHandler is associated with.
-        ThemedHandler
-        // TestData returns a list of example data used for testing if a theme renders correctly.
-        TestData() []TestBundle
-}
-
-// TestBundle is a template arg associated with a description used for testing.
-type TestBundle struct {
-        // Description is a short one line description of what the data contains.
-        Description string
-        // Data is the data fed directly into the template.
-        Data templates.Args
-}