[milo] Add BuildSummary and common models.

milo/appengine/common/model/patch_info.go

Index: milo/appengine/common/model/patch_info.go
diff --git a/milo/appengine/common/model/patch_info.go b/milo/appengine/common/model/patch_info.go
new file mode 100644
index 0000000000000000000000000000000000000000..01bef3e22025e39d21f5117e8358374eeae957b2
--- /dev/null
+++ b/milo/appengine/common/model/patch_info.go
@@ -0,0 +1,14 @@
+// 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 model
+
+// PatchInfo provides information about a patch included in a build.
+type PatchInfo struct {
+	// A link to the patch page (i.e. the gerrit/rietveld review page).
+	Link Link
+
+	// The email of the author of the Patch.
+	AuthorEmail string
+}