Add web_manifest_url in WebappInfo.

chrome/android/webapk/shell_apk/BUILD.gn

 # Copyright 2015 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.
 
 import("//build/config/android/rules.gni")
 
 declare_args() {
   # The origin URL of the WebAPK. Used to generate a unique package name for
   # WebAPK. Example: "foo.com"
   webapk_manifest_package_origin = "template"
 
   # The browser that the WebAPK will be bound to.
   webapk_runtime_host = "com.google.android.apps.chrome"
 
+  # The Url of the Web Manifest file.
+  webapk_web_manifest_url = "https://www.template.com/manifest.json"
+
   # Attributes from Web Manifest.
   webapk_start_url = "https://www.template.com/home_page"
   webapk_name = "Longer Sample WebAPK Name"
   webapk_short_name = "Sample WebAPK"
   webapk_scope_url = "https://www.template.com"
   webapk_display_mode = "standalone"
   webapk_orientation = "portrait"
   webapk_theme_color = "4288230399L"  #0xFF9933FF
   webapk_background_color = "4291624959L"  #0xFFCCFFFF
 
@@ skipping 19 matching lines @@
     "start_url=$webapk_start_url",
     "name=$webapk_name",
     "short_name=$webapk_short_name",
     "scope_url=$webapk_scope_url",
     "display_mode=$webapk_display_mode",
     "orientation=$webapk_orientation",
     "theme_color=$webapk_theme_color",
     "background_color=$webapk_background_color",
     "icon_url=$webapk_icon_url",
     "scope_url_host=$webapk_scope_url_host",
+    "web_manifest_url=$webapk_web_manifest_url",
   ]
 }
 
 android_resources("shell_apk_resources") {
   resource_dirs = [ "res" ]
   custom_package = "org.chromium.webapk.shell_apk"
 }
 
 android_library("dex_loader_java") {
   java_files = [ "src/org/chromium/webapk/shell_apk/DexLoader.java" ]
@@ skipping 32 matching lines @@
       [ "javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java" ]
   deps = [
     ":dex_loader_java",
     "//base:base_java",
     "//base:base_java_test_support",
     "//chrome/android/webapk/libs/common:common_java",
     "//content/public/test/android:content_java_test_support",
   ]
   srcjar_deps = [ "javatests/dex_optimizer:dex_optimizer_service_aidl" ]
 }