The current setup builds on Linux and ChromeOS. All files get Linux Xrefs, and files unique to ChromeOS get ChromeOS Xrefs. However, there is no merging of Xrefs, and any file with Xrefs for both platforms only get the Linux Xrefs. 

Getting support for more platforms is on the roadmap, starting with better integration between the two platforms we currently are building for (crbug/652215). Next after that we plan to add more platforms and merge them in as well. Android would likely be the platform after ChromeOS given that there is already some started work on this by akuegel@. Then after that, there it would be Windows and then Mac. 

With the current setup, adding a new builder for a platform will provide Xrefs for files unique to that platform.

I don't know much about how the Xrefs work, so I don't think I followed comment #1.

Are you saying that if a file is only used on CrOS, the xrefs in that file work, but if a file is used on both desktop Linux and CrOS, only the xrefs that apply to both platforms or the ones that are desktop-only (not CrOS) work? So, no xref in something #ifdef'ed OS_CHROMEOS ? It seemed like the latter also worked for me just now.

Sorry about to confusion. 

The recipe for the code search builder has this filtering step: https://cs.chromium.org/chromium/build/scripts/slave/recipes/chromium_codesearch.py?rcl=0&l=174 calling https://cs.chromium.org/chromium/build/scripts/slave/chromium/filter_compilations.py?dr=C&q=filter_compilations&sq=package:chromium&l=1. For ChromeOS, the set of compilation units for Linux is subtracted from the set of compilation units for ChromeOS. Xrefs are computed for the remaining set of compilation units, resulting in Xrefs on only ChromeOS specific compilation units. 

All this is because there is currently no support for merging of Xrefs, but I'll be investigating if we can support this.

I'm curious about the Xrefs in "#ifdef OS_CHROMEOS"-code you mentioned. Could you give an example?

> I'm curious about the Xrefs in "#ifdef OS_CHROMEOS"-code you mentioned. 
> Could you give an example?

Of course, now I can't remember what I was looking at :). I tried a few examples and they don't seem cross-referenced now, so maybe I was just confused.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/518af60059cef138b41ca6b4f3d65c2a8915f50e

commit 518af60059cef138b41ca6b4f3d65c2a8915f50e
Author: Adam Chyb <achyb@chromium.org>
Date: Tue Jan 10 03:31:07 2017

Added android config to chromium codesearch index pack builder

BUG= 662136 ,  643026 , 526154

Change-Id: Ife153e003cdc0ea57f9cebada6b5017d91ff966d
Reviewed-on: https://chromium-review.googlesource.com/426458
Reviewed-by: Emma Söderberg <emso@chromium.org>
Commit-Queue: Adam Chyb <achyb@chromium.org>

[add] https://crrev.com/518af60059cef138b41ca6b4f3d65c2a8915f50e/scripts/slave/recipes/chromium_codesearch.expected/full_Chromium_Android_Codesearch.json
[add] https://crrev.com/518af60059cef138b41ca6b4f3d65c2a8915f50e/scripts/slave/recipes/chromium_codesearch.expected/full_Chromium_Android_Codesearch_Builder.json
[modify] https://crrev.com/518af60059cef138b41ca6b4f3d65c2a8915f50e/scripts/slave/recipes/chromium_codesearch.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/e6aead043608dd9e421106eaf4d1ba7b1a295f70

commit e6aead043608dd9e421106eaf4d1ba7b1a295f70
Author: Adam Chyb <achyb@chromium.org>
Date: Mon Jan 16 03:46:48 2017

Added a builder to create index packs for the Android build of Chromium

BUG= 662136 ,  643026 , 526154

Change-Id: Icc2f8bc57c5fa7d49dacfd9fd22476d768311b04
Reviewed-on: https://chromium-review.googlesource.com/426284
Reviewed-by: Dave Sansome <dsansome@chromium.org>
Reviewed-by: Phil Wright <philwright@chromium.org>
Commit-Queue: Adam Chyb <achyb@chromium.org>

[modify] https://crrev.com/e6aead043608dd9e421106eaf4d1ba7b1a295f70/masters/master.chromium.infra.cron/master.cfg
[modify] https://crrev.com/e6aead043608dd9e421106eaf4d1ba7b1a295f70/masters/master.chromium.infra.cron/slaves.cfg