Markdown extension / webview: Focus border

[kieferrm]

1. Using the markdown extension (Extract the MarkDown editor into an extension #6106) open a preview of a markdown file
2. Open command pallet
3. Close pallet by clicking into the preview
   -> focus border

I haven't found a styling yet that solves the issue.

[bpasero]

When quick open is closing it calls the focus() method of the active editor. It is up to the implementor of the editor (in this case the htmlPreviewPart) to do something then. We seem to call focus() on the and this brings up the native outline.

If we add a rule to our shell.css (in https://github.com/Microsoft/vscode/blob/master/src/vs/workbench/electron-browser/media/shell.css#L174) to have no outline for webviews, this issue is fixed.

.monaco-shell .part.editor .iframe-container,
.monaco-shell .part.editor .binary-container,
webview {
    outline: 0 !important;
}

[jrieken]

This fix should go in the previewPart

[kieferrm]

The change is not working since the outline style is not applied to the webview but to the body of the displayed document(s).