Code review comment for lp:~osomon/oxide/maxCacheSize

I added the DCHECK in BrowserContextIOData as suggested.

I see two problems with moving the Qt port check to WebContextAdapter though:

 - (minor) the warning message cannot mention "WebContext.maxCacheSizeHint" as we’re not guaranteed the class and property would be called like this in a QtWidgets port

 - maxCacheSizeHintChanged() would still be emitted from the QML API even if an integer overflow (or a value < 0) was detected and the size hint was not actually changed, unless we change the signature of WebContextAdapter::setMaxCacheSizeHint(…) to return a boolean indicating success