Add a flag that lets the webstore show a different UI on app install.

chrome/test/data/extensions/api_test/webstore_private/app_install_bubble.js

Index: chrome/test/data/extensions/api_test/webstore_private/app_install_bubble.js
diff --git a/chrome/test/data/extensions/api_test/webstore_private/app_install_bubble.js b/chrome/test/data/extensions/api_test/webstore_private/app_install_bubble.js
new file mode 100644
index 0000000000000000000000000000000000000000..d1ac1b8e3311863b0b3321a98a328c2ba6b5b3dc
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/webstore_private/app_install_bubble.js
@@ -0,0 +1,25 @@
+// Copyright (c) 2011 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.
+
+var tests = [
+  function appInstallBubble() {
+    // See things through all the way to a successful install.
+    listenOnce(chrome.management.onInstalled, callbackPass(function(info) {
+      assertEq(info.id, appId);
+    }));
+
+    var manifest = getManifest("app/manifest.json");
+    // Begin installing.
+    chrome.webstorePrivate.beginInstallWithManifest2(
+        {'id': appId,'manifest': manifest, 'appInstallBubble':true},
+        callbackPass(function(result) {
+      assertEq(result, "");
+
+      // Now complete the installation.
+      chrome.webstorePrivate.completeInstall(appId, callbackPass());
+    }));
+  }
+];
+
+runTests(tests);