Ensure CefSettings.CachePath and RequestContextSettings.CachePath are absolute

[amaitland]

The cache path must be an absolute path. It was never intended to work with relative paths.

As per https://bitbucket.org/chromiumembedded/cef/issues/2916/not-persisting-in-local-stoage-when-using#comment-56993126 the CachePath must be absolute.

• throw Exception if paths are non absolute

Related issue #3074

[amaitland]

Another option would be to validate the path provided and throw an exception. This may be the slightly less user friendly option, it would avoid any potential issues where the Path.GetFullPath was to resolve incorrectly.

https://docs.microsoft.com/en-us/dotnet/api/system.io.path.ispathrooted?view=netframework-4.8

[amaitland]

Browsersubprocess must also be absolute now

https://bitbucket.org/chromiumembedded/cef/commits/dede95c5866fee73db7fb0e5f2077fb2135db6ac

[amaitland]

The exception in https://github.com/cefsharp/CefSharp/blob/master/CefSharp.Core/Cef.h#L204 should be updated to make it clear an absolute path is required also.

[amaitland]

Resolved in 98b7abe

[terry-alphasoftware]

The absolute path check on Windows is incorrect in both Chromium and the matching code in CefSharp. A path does not need to start with a drive letter on Windows. A UNC path is a valid absolute path. See System.Path.IsPathFullyQualified().

My use of CefSharp was using the user's profile path as the cache location. System.Environment.GetFolderPath(System.Environment.SpecialFolder.MyDocuments) returns a UNC path on one of our customer's machine, which then triggers the absolute path exception.

I am able to work around this problem, but am writing this here for future reference.