Removed the code that used to truncate the output file in
FileWriterDelegate. There is no need for that. FileWriterDelegate is
only getting passed empty files to start with. The passed file is either
a freshly created one, or it is a reused temporary file that just got
truncated [1].

[1] https://source.chromium.org/chromium/chromium/src/+/main:chrome/common/safe_browsing/zip_analyzer.cc;l=64;drc=e2cba64c183ae17816143ee344e6f7c81451555a

BUG=None
TEST=autoninja -C out/Default zlib_unittests && out/Default/zlib_unittests
TEST=autoninja -C out/Default components_unittests && out/Default/components_unittests --gtest_filter='UnzipTest.*'

Change-Id: Ib3551029e18d84f6e8585d8662fed9466a023207
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3512049


Reviewed-by: Noel Gordon <noel@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/main@{#980411}
NOKEYCHECK=True
GitOrigin-RevId: 96875c3d1aca80f2384a4004d711dbdc87df3a86