Request upgraded WebAPK from WebAPK server if the ShellAPK version changes

chrome/android/webapk/shell_apk/shell_apk_version.gni

Index: chrome/android/webapk/shell_apk/shell_apk_version.gni
diff --git a/chrome/browser/android/webapk/BUILD.gn b/chrome/android/webapk/shell_apk/shell_apk_version.gni
similarity index 53%
copy from chrome/browser/android/webapk/BUILD.gn
copy to chrome/android/webapk/shell_apk/shell_apk_version.gni
index 6bcd0ac4dc479305465907faf565904972b09a00..f91c1506497d9fd4357a1dee85eb2efac8fd1356 100644
--- a/chrome/browser/android/webapk/BUILD.gn
+++ b/chrome/android/webapk/shell_apk/shell_apk_version.gni
@@ -2,10 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//third_party/protobuf/proto_library.gni")
-
-proto_library("proto") {
-  sources = [
-    "webapk.proto",
-  ]
-}
+# Must be incremented whenever code in //chrome/android/webapk/shell_apk
+# (including AndroidManifest.xml) is updated.
+shell_apk_version = 1