Remove TryGetCefMainFrame method - now just using calls directly to GetMainFrame() (brings code more inline with cefclient example)
Remove TryGetCefHost method - similar cleanup to previous commit, brings code more inline with cefclient example
(It would appear that having an instance of the browser then there will always to be a host)
Switch back to tabbed winforms example being the default (maybe one day create a method to switch between the two)
Fix comment formatting
Remove `this.` - no need
Simplify ScreenshotAsync, now just uses a TaskCompletionSource
Expand OffScreen Example to include an example of capturing the first offscreen image (currently the first image is blank, though I'm thinking that's probably expected)
This allows for testing of the updated ScreenshotAsync method
Remove the second lock in InvokeRenderAsync - now using the same lock object for GdiBitmap
Slight code simplification in OffScreen.Example