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On Windows, when downloading the second or later part of a multipart
archive, unrar will attempt to open another file. Due to the
modifications we place on unrar to work within the sandbox, we
don't open the file, but instead use File::hOpenFile as the handle.
This is uninitialized memory, which is passed to GetFileType, causing
a crash.

This CL initializes hOpenFile to fix this problem and adds a test that
would have caught the issue.

Fixed: 1135503
Change-Id: I6cc83a5a2b5925900cde7b8b2dc8be64f0620d21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490334
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820896}