"blob_storage/" and "webrtc_event_logs/" directories are created in current working directory when using in-memory cache

This issue doesn't occur if you set `ApplicationSettings.cache_path` option.

Upstream CEF issue:
https://bitbucket.org/chromiumembedded/cef/issues/2289/cefclient-creates-permanent-cache

The "GPUCache/" directory may be fixed by adding a command line switch `--disable-gpu-shader-disk-cache`, Issue #419 is to fix that.