Get launching right for Chrome extensions

[ussuri]

Launching via the 'Run' button doesn't work for Chrome extensions: we need to fix that. Once done, the Chrome extension sample should be moved out from under the showWipProjectTemplates dev flag in spark_polymer_ui.html.

[ussuri]

Currently, the following message appears:

We could:

• Analyze manifest.json
• Determine app-vs-extension based on the presence of "app" key
• Install in Chrome
• If an app, launch
• If an extension, open tab in Chrome at chrome://extensions/?id=<extension ID>

[ussuri]

To avoid surprises, copying from #1704:

The "Chrome extension" project type has been moved under a dev flag "wip-project-templates". To enable the flag in the downloaded version of the app, add a file named .spark.json to your top-level project directory, with the following contents:

{
  "wip-project-templates": true
}

Then restart Spark.

Note that Spark needs to know that the above-mentioned directory is your top-level project location. For that to happen, if you just downloaded the app, you will have to create at least one project (a blank one will do). In the process of project creation, Spark will ask you to choose the top-level project location.

[dinhvh]

Fixed.

[ussuri]

It's been just hidden under a flag, not fixed.

[DanielHerr]

The run button should open chrome-extension://id/popup.html, or whatever the browser or page action popup from the manifest is.