Plumb site engagement to the renderer process.

third_party/WebKit/public/platform/site_engagement.mojom

Index: third_party/WebKit/public/platform/site_engagement.mojom
diff --git a/third_party/WebKit/public/platform/site_engagement.mojom b/third_party/WebKit/public/platform/site_engagement.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..831bed6b62ccf3e3d6e2855e930592587b285138
--- /dev/null
+++ b/third_party/WebKit/public/platform/site_engagement.mojom
@@ -0,0 +1,21 @@
+// Copyright 2016 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.
+
+module blink.mojom;
+
+import "url/mojo/origin.mojom";
+
+enum EngagementLevel {
+  NONE,
+  MINIMAL,
+  LOW,
+  MEDIUM,
+  HIGH,
+  MAX,
+};
+
+interface EngagementClient {
+  // The browser tells the renderer the engagement level of the current URL.

[nasko, 2016/11/30 18:00:25]

nit: Let's avoid using the word "current" as it is not very clear. Also, this
API can probably be called with arbitrary origin, so there is no enforcement
that the origin is the current one. Last, the parameter is an origin, not an URL
:).

[dominickn, 2016/11/30 23:46:33]

Done.

+  SetEngagementLevel(url.mojom.Origin origin, EngagementLevel level);
+};