winrt: Use native file dialog

The native Windows Runtime file picker is required to support picking
of any file/folder from the system. Due to platform security restrictions,
the non-native file dialog is effectively useless when outside of the
application's installation or local storage directories.

This adds a QPA implementation for the WinRT file picker, as well as
a simple file system engine to handle files which were opened by the
picker. This necessary for platform security reasons, as it is not
possible to open files from arbitrary paths - only file handles opened by
the picker can be used, so these are kept inside this file system engine
and acted upon when a known path is observed.

The file system engine is only instantiated when needed, and may prove
useful for other areas of Qt (such as known folders/standard paths) which
must operate on a virtual file rather than an absolute path.

Task-number: QTBUG-37748
Change-Id: Ia4fd6c5065ac92101ce34adcb6c9026fbcff56df
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>

0 files changed, 0 insertions, 0 deletions