[milo] Refactor all html knowledge out of backends.

milo/frontend/view_build.go

+// Copyright 2017 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.
+
+package frontend
+
+import (
+        "github.com/luci/luci-go/milo/buildsource"
+        "github.com/luci/luci-go/server/router"
+        "github.com/luci/luci-go/server/templates"
+)
+
+// BuildHandler is responsible for taking a universal build ID and rendering the
+// build page (defined in ./appengine/templates/pages/build.html).
+func BuildHandler(c *router.Context, buildID buildsource.ID) {
+        build, err := buildID.Get(c.Context)
+        // TODO(iannucci, hinoka): make MiloBuild refer to annotation stream by
+        // host/prefix/path instead of by directly pulling it. Do all annotation
+        // stream rendering in the frontend.
+        if err != nil {
+                ErrorHandler(c, err)
+        } else {
+                templates.MustRender(c.Context, c.Writer, "pages/build.html", templates.Args{
+                        "Build": build,
+                })
+        }
+}