Add chrome://site-engagement WebUI.

chrome/browser/ui/webui/engagement/site_engagement.mojom

Index: chrome/browser/ui/webui/engagement/site_engagement.mojom
diff --git a/chrome/browser/ui/webui/engagement/site_engagement.mojom b/chrome/browser/ui/webui/engagement/site_engagement.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..b53e25d5e411f3e5809230185fe9be02d439a20a
--- /dev/null
+++ b/chrome/browser/ui/webui/engagement/site_engagement.mojom
@@ -0,0 +1,16 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+struct SiteEngagementInfo {
+  string origin;
+  int32 score;
+};
+
+interface SiteEngagementUIHandlerMojo {
+  GetSiteEngagementInfo(SiteEngagementPage page);
+};
+
+interface SiteEngagementPage {
+  HandleSiteEngagementInfo(array<SiteEngagementInfo> info);

[Sam McNally, 2015/08/26 08:23:22]

Is this called more than once?

If not, you can make |info| a return value for GetSiteEngagementInfo:
GetSiteEngagementInfo() => (array<SiteEngagementInfo> info);

The JS binding for that pattern is a function that returns a promise to a
dictionary containing an |info| field (mojo supports multiple return values,
unlike JS promises).

[calamity, 2015/09/08 07:30:06]

It most likely will be at some point. We would want the page to update when
someone presses a button, for example.

+};