Initial CL for talking to the WebAPK server to generate WebAPK

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

+// 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;
+
+/**
+ * Interface for installing WebAPKs.
+ */
+public interface WebApkInstaller {
+    /**
+     * Installs a WebAPK.
+     * @param filePath File to install.
+     * @param packageName Package name to install WebAPK at.
+     * @return True if the install was started. A "true" return value does not guarantee that the
+     *         install succeeds.
+     */
+    boolean installAsync(String filePath, String packageName);
+}