Implement <appview>

extensions/common/api/app_runtime.idl

Index: extensions/common/api/app_runtime.idl
diff --git a/extensions/common/api/app_runtime.idl b/extensions/common/api/app_runtime.idl
index b094c98dade73479514b0204537deb187f90b21f..cc6f87e3f08b2c165fba0b2d5bb281e142baac67 100644
--- a/extensions/common/api/app_runtime.idl
+++ b/extensions/common/api/app_runtime.idl
@@ -42,7 +42,20 @@ namespace app.runtime {
     boolean? isKioskSession;
   };
 
+  [inline_doc] dictionary AppEmbeddingRequest {
+    long? id;
+
+    DOMString embedderExtensionId;
+
+    [nocompile] static void allow(DOMString url, object api, DOMString schema);
+
+    [nocompile] static void deny();
+  };
+
   interface Events {
+    // Fired when an embedding app requests to embed this app.
+    static void onAppEmbeddingRequest(AppEmbeddingRequest request);
+
     // Fired when an app is launched from the launcher.
     static void onLaunched(optional LaunchData launchData);