WebAPK: Move MainActivity#onCreate() to runtime library

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"
@@ skipping 53 matching lines @@
 }
 
 # Template for WebAPK. When a WebAPK is generated:
 # - Android manifest is customized to the website.
 # - App icon is extracted from the website and added to the APK's resources.
 android_apk("webapk") {
   android_manifest = shell_apk_manifest
   android_manifest_dep = ":shell_apk_manifest"
   apk_name = "WebApk.$webapk_manifest_package_origin"
   java_files = [
+    "src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java",
     "src/org/chromium/webapk/shell_apk/MainActivity.java",
     "src/org/chromium/webapk/shell_apk/WebApkSandboxedProcessService.java",
     "src/org/chromium/webapk/shell_apk/WebApkSandboxedProcessService0.java",
     "src/org/chromium/webapk/shell_apk/WebApkSandboxedProcessService1.java",
     "src/org/chromium/webapk/shell_apk/WebApkSandboxedProcessService2.java",
     "src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java",
   ]
   deps = [
     ":dex_loader_java",
     ":shell_apk_resources",
@@ skipping 12 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" ]
 }