Reland "Fix ifdef guard for OS_CHROMEOS."

This reverts commit 2133e7d7.

Reason for revert: The original revert was speculative. Relanding.

Original change's description:
> Revert "Fix ifdef guard for OS_CHROMEOS."
>
> This reverts commit fcffa1cc.
>
> Reason for revert: Reverting due to failure on Linux ASAN LSAN bot
> See link below for failure details:
> https://ci.chromium.org/p/chromium/builders/ci/Linux%20ASan%20LSan%20Tests%20%281%29/82545
>
> Original change's description:
> > Fix ifdef guard for OS_CHROMEOS.
> >
> > There's on going work to unset OS_LINUX on Chrome OS build,
> > however, it is not yet completed, so it is still defined.
> >
> > This CL adds the explicit !defined(OS_CHROMEOS) to fix
> > the behavior.
> >
> > Bug: 1110266
> > Test: Built locally.
> > Change-Id: I60731672aabb6bb6025e29a0b641988e68ecade5
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2460826
> > Auto-Submit: Hidehiko Abe <hidehiko@chromium.org>
> > Commit-Queue: Guido Urdaneta <guidou@chromium.org>
> > Reviewed-by: Guido Urdaneta <guidou@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#815116}
>
> TBR=hidehiko@chromium.org,guidou@chromium.org
>
> Change-Id: I59d4a9dfe96d45199c87fcf42a65d9e05e7b76d1
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1110266
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462015
> Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
> Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#815138}

TBR=hidehiko@chromium.org,guidou@chromium.org,tluk@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1110266
Change-Id: I086c838a52603f647d5dbc948e577e930d80ecd1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466008Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Auto-Submit: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816211}

chrome/browser/media/webrtc/webrtc_log_uploader.cc

@@ -347,7 +347,7 @@ void WebRtcLogUploader::SetupMultipart(
   const char product[] = "Chrome";
 #elif defined(OS_MAC)
   const char product[] = "Chrome_Mac";
-#elif defined(OS_LINUX)
+#elif defined(OS_LINUX) && !defined(OS_CHROMEOS)
 #if !defined(ADDRESS_SANITIZER)
   const char product[] = "Chrome_Linux";
 #else