Chrome talks to Play to install WebAPKs.

chrome/android/java/src/org/chromium/chrome/browser/webapps/GooglePlayWebApkInstallDelegate.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/GooglePlayWebApkInstallDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/GooglePlayWebApkInstallDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/GooglePlayWebApkInstallDelegate.java
new file mode 100644
index 0000000000000000000000000000000000000000..f790dd47a9df612ff7427301849a32e61fb05b5a
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/GooglePlayWebApkInstallDelegate.java
@@ -0,0 +1,52 @@
+// 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.
+
+package org.chromium.chrome.browser.webapps;
+
+import android.support.annotation.IntDef;
+
+import org.chromium.base.Callback;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Defines an interface for installing WebAPKs via Google Play.
+ */
+public interface GooglePlayWebApkInstallDelegate {

[dominickn, 2016/12/08 03:31:26]

Can this just be the PlayWebApkInstaller? Or some other name that doesn't
involve InstallDelegate? WebApkInstaller.java already has an InstallerDelegate
to monitor the installation status of an APK, and I found myself getting
confused with the two.

[Xi Han, 2016/12/08 18:03:07]

PlayWebApkInstallClientInterface? The delegate is a "singleton" object that the
WebApkInstaller can delegate the install/update task to. Ideally it should be a
subclass of WebApkInstaller, but the singleton design of this delegate makes it
impossible to subclass without big refactoring of WebApkInstaller, because we
create new WebApkInstaller object for every install/update request. Therefore,
we need to name it something different than Installer.

+    /**
+     * The app state transitions provided by Google Play during download and installation process.
+     */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef({INVALID, DOWNLOAD_PENDING, DOWNLOADING, DOWNLOAD_CANCELLED, DOWNLOAD_ERROR,
+             INSTALLING, INSTALL_ERROR, INSTALLED})
+    public @interface InstallerPackageEvent {}
+    public static final int INVALID = -1;
+    public static final int DOWNLOAD_PENDING = 0;
+    public static final int DOWNLOADING = 1;
+    public static final int DOWNLOAD_CANCELLED = 2;
+    public static final int DOWNLOAD_ERROR = 3;
+    public static final int INSTALLING = 4;
+    public static final int INSTALL_ERROR = 5;
+    public static final int INSTALLED = 6;
+
+    /**
+     * Uses Google Play to install WebAPK asynchronously.
+     * @param packageName The package name of WebAPK to install.
+     * @param version The version of WebAPK to install.
+     * @param title The title of the WebAPK to display during installation.
+     * @param token The token from WebAPK Minter Server.

[dominickn, 2016/12/08 03:31:26]

Missing an @param for callback

[Xi Han, 2016/12/08 18:03:07]

Done.

+     * @return True if the install was started. A "true" value does not guarantee that the install
+     *         succeeds.
+     */
+    boolean installAsync(String packageName, int version, String title, String token,
+            Callback<Boolean> callback);
+
+    /**
+     * Calls the callback once the installation either succeeded or failed.
+     * @param packageName The package name of WebAPK for the installation.
+     * @param event The result of the install.
+     */
+    void onGotInstallEvent(String packageName, @InstallerPackageEvent int event);
+}