Revert "[chromebox_for_meetings] Don't drop characters from lines"

This reverts commit 20281ac1.

Reason for revert: Suspected for causing consistent test failures on  linux-cfm-rel builder
i.e. https://ci.chromium.org/ui/p/chromium/builders/ci/linux-cfm-rel/58143/overview

Original change's description:
> [chromebox_for_meetings] Don't drop characters from lines
>
> The GetCurrentOffset() function was written to support
> getting the current file offset, even if the file is at
> an EOF, which would normally cause tellg() to return -1.
> To handle the EOF case, we were performing the following
> routine: clear EOF bit -> tellg() -> .get() to re-trigger
> the EOF bit. It was falsely determined that the .get()
> call would be safe and not advance the read pointer, but
> in very specific cases, this causes some log lines to have
> their leading character dropped, which leads to a malformed
> timestamp and effectively drops the log.
>
> Instead of this hacky process, we can track the last known
> read offset in a member variable and treat it as the current
> offset when we've reached an EOF. This logic works because
> tellg() will only report a -1 *after* we attempt a read that
> contains no data; if we call tellg() after reading the last
> line, but before calling getline() again, it will report the
> correct offset.
>
> Bug: b:343965002
> Change-Id: Icd43161c3c1114302c88b1fbc151198be05674f4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5589844


> Auto-Submit: Niko Tsirakis <ntsirakis@google.com>
> Reviewed-by: Kyle Williams <kdgwill@chromium.org>
> Commit-Queue: Kyle Williams <kdgwill@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1310785}

Bug: b:343965002
Change-Id: I7a3e14e4a6ea1dca6e68531cfdaa62c0b4639d24
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5599845
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Georg Neis <neis@chromium.org>
Auto-Submit: Nidhi Jaju <nidhijaju@chromium.org>
Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1311057}