>> Also, I'm not actually sure I was write that we'd need to load the webapk in 
>> background tab like I was saying in #2. Does the manifest provide enough
>> information that we could just fetch it and check? I guess we still wouldn't 
>> want to request/parse the manifest from the browser process so it's not that 
>> simple?

Forcing an update from chrome://webapks would be kind of tricky because the update logic expects a parsed manifest. Currently, Chrome is set up to only download the manifest for the current page content/renderer/manifest/manifest_manager.cc so we would need to refactor the logic