No progress while opening PR

[dmitrivMS]

Testing microsoft/vscode#274805

Repro Steps

1. Open VS Code Insiders
2. Load vscode repo
3. From a browser open
   vscode-insiders://github.vscode-pull-request-github/checkout-pull-request?%7B%22owner%22%3A%22microsoft%22%2C%22repo%22%3A%22vscode%22%2C%22pullRequestNumber%22%3A273860%7D

Actual Result
You are looking at VS Code apparently doing nothing for seconds, eventually there is something in the status bar (hard to notice), and much later PR view shows up.

Expected Result
Either open PR pane and show progress there or show notification window with progress if it's taking this long.

[dmitrivMS]

Progress is now shown.

[alexr00]

@dmitrivMS thanks for all the great issues!