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This CL removes usage of LzmaFileAllocator and tries to write unpack
result directly in the output file.
When uncompressing a folder that maps directly to a file, this is
possible and a memory mapping is used. In practice, this is always
the case. Support for folder containing multiple files is kept as
fallback and uses a pre-allocated file buffer, which is then copied in
individual files.

For running full setup install from chrome.packed.7z (Kb)
Before:
Setup.Install.PeakPagefileUsage 19748
Setup.Install.PeakWorkingSetSize 250528
GetCumulativeDiskUsageInBytes 761134
After:
Setup.Install.PeakPagefileUsage 19720
Setup.Install.PeakWorkingSetSize 250512
GetCumulativeDiskUsageInBytes 297818

The difference in memory is not significant, but improvement
are expected mostly for disk usage.

Bug: 933975
Change-Id: I26c1b118fc512d2caaa8112d3da37e6db460486b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1845956
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709940}