The file in question does not seem to be known to grok (the cross-reference server), which means it is getting lost somewhere on the way. I verified that the file with the Xrefs is known to grok. 

Basically the following should happen: a compilation database is extracted (using ninja), this is fed to a program translating compilation units to entries in an index pack sent to grok. This index pack includes generated files.

The builder is green, so that is not the issue. I'm not seeing the file listed in the compilation database extracted by ninja, but I'm actually not seeing either of the files mentioned listed in the compilation db.

Could this be a configuration issue? We are currently displaying a Linux 'all' configuration, along with ChromeOS 'all' Xrefs for files unique to ChromeOS. The two files are listed together in src/media/BUILD.gn, so I'm not sure this is connected to the configuration.

https://cs.chromium.org/chromium/src/media/filters/ffmpeg_demuxer_unittest.cc?rcl=0&l=31 include the header with Xrefs. My guess is that this is causing a index pack entry to be included for that header. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/469e5455e27a88f28e4e7154922c2539446e1413

commit 469e5455e27a88f28e4e7154922c2539446e1413
Author: Emma Soederberg <emso@chromium.org>
Date: Tue Dec 06 11:50:32 2016

More logging of index pack creation

BUG= 671546 

Change-Id: I66f3008076ac12529b9ec0c9336f449b4f17c92d
Reviewed-on: https://chromium-review.googlesource.com/416411
Commit-Queue: Emma Söderberg <emso@chromium.org>
Reviewed-by: Paweł Hajdan Jr. <phajdan@google.com>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>

[modify] https://crrev.com/469e5455e27a88f28e4e7154922c2539446e1413/scripts/slave/chromium/package_index.py

The added logging verifies that media/formats/mp4/avc.h is pulled in because it is needed by media/filters/ffmpeg_demuxer_unittest.cc: https://build.chromium.org/p/chromium.infra.cron/builders/Chromium%20Linux%20Codesearch/builds/3485/steps/create%20index%20pack/logs/stdio

That is, this is a configuration issues. When compiling for Linux (or ChromeOS) using the 'all' target, the other files in media/formats/mp4 are not included by themselves or needed by included files. 

We are working on better support for multiple configurations. If you have a suggestion for configurations you would like to see support for in code search please let us know.