[WebAPK] Launch Play Store if the user does not have any web browsers installed

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 113 matching lines @@
     ":webapk_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" ]
 }
 
 junit_binary("webapk_shell_apk_junit_tests") {
-  java_files = [ "junit/src/org/chromium/webapk/shell_apk/HostBrowserClassLoaderTest.java" ]
+  java_files = [
+    "junit/src/org/chromium/webapk/shell_apk/HostBrowserClassLoaderTest.java",
+    "junit/src/org/chromium/webapk/shell_apk/MainActivityTest.java",
+  ]
   deps = [
     ":webapk_java",
     "//chrome/android/webapk/libs/common:common_java",
   ]
 }