Reland of [WebAPKs] Make WebAPK update flow more sensible

chrome/android/webapk/shell_apk/shell_apk_version.gni

Index: chrome/android/webapk/shell_apk/shell_apk_version.gni
diff --git a/chrome/android/webapk/shell_apk/shell_apk_version.gni b/chrome/android/webapk/shell_apk/shell_apk_version.gni
index 46d2071059ad74cfdb0e9b083e92f6651a5bff65..c4d66ff1992df3516f9c88b69d6db437168908f1 100644
--- a/chrome/android/webapk/shell_apk/shell_apk_version.gni
+++ b/chrome/android/webapk/shell_apk/shell_apk_version.gni
@@ -3,5 +3,13 @@
 # found in the LICENSE file.
 
 # Must be incremented whenever code in //chrome/android/webapk/shell_apk
-# (including AndroidManifest.xml) is updated.
-shell_apk_version = 3
+# (including AndroidManifest.xml) is updated. This version should be incremented
+# prior to uploading a new ShellAPK to the WebAPK Minting Server.
+# Does not affect Chrome.apk
+template_shell_apk_version = 4
+
+# The ShellAPK version expected by Chrome. Chrome will try to update the WebAPK
+# if the WebAPK's ShellAPK version is less than |expected_shell_apk_version|.
+# The version should be incremented after a new ShellAPK has been uploaded to
+# the WebAPK Minting Server.
+expected_shell_apk_version = 3