Devlin, do you know what the correct behavior is here?

Hmm... I'm a bit confused - isn't knipolnnllmklapflnccelgolnpehhpl a platform app?  In which case these steps don't really make sense (it shouldn't have an icon near the omnibox).

Use nckgahadagoaajjgafhacjanaoiihapd for the extension version. Must've copied the wrong ID.

Windows has a similar problem:

1. Open Hangouts extension window
2. Right-click Taskbar icon, click "Google Hangouts" => opens chrome://extensions in new tab

Pinning that icon, then closing the Hangouts window, clicking the icon will open chrome://extensions.

Interesting.  I wonder if this is related to panels?  Most extensions won't have a task bar/shelf entry - opening an extension tab/window/popup would just be a chrome window.

Can you take a screenshot of the menu on CrOS and attach it?  (For posterity and code hunting purposes)

attached screenshots of hangouts extension window's shelf icon's context menu, with hangouts extension action button visible in extensions toolbar near omnibox:

* hangouts.png - context menu when extension window is open
* hangouts_pinned_close.png - context menu when shelf icon is pinned and extension window is not open

Deleted: hangouts.png 58.2 KB

	hangouts.png 58.2 KB View Download

Deleted: hangouts_pinned_closed.png 4.9 KB

	hangouts_pinned_closed.png 4.9 KB View Download

uhh the 2nd screenshot only clipped the context menu itself, but that works too. I didn't know we could do that!

My suspicion is that we're hitting this line:
https://chromium.googlesource.com/chromium/src/+/e657f3fad1c922ab7af0ff2d6faba42403296195/chrome/browser/ui/extensions/application_launch.cc#164

  // For extensions lacking launch urls, determine a reasonable fallback.
  if (!url.is_valid()) {
    url = extensions::OptionsPageInfo::GetOptionsPage(extension);
    if (!url.is_valid())
      url = GURL(chrome::kChromeUIExtensionsURL);
  }

hangouts doesn't have a launch url, or an options url, so we just open chrome extensions.

I agree with your initial hunch that we just shouldn't even have "New tab" available as an option.  Extensions can't be launched.

Ideally, we can just modify ExtensionAppContextMenu to exclude all app-like items if the underlying item is an extension and not an app.  I'm not sure if there's any other circumstances (other than panels) where we'd show an extension there, though - maybe stevenjb@ knows?

I think we should support this use case, given the deprecation of platform apps. Pinned shortcuts for extensions that launch windows should be able to launch an extension window. It could be feasible to use manifest option like "launch_url", or make pinned icons trigger the extension's browser_action.

Devlin, WDYT?