When doing official gn builds on my local machine I consistently hit syzygy errors on chrome.dll and chrome_child.dll. Typical errors look like this:

FAILED: syzygy/chrome.dll syzygy/chrome.dll.pdb 
C:/src/depot_tools/python276_bin/python.exe ../../chrome/tools/build/win/syzygy/reorder.py --input_executable chrome.dll --input_symbol chrome.dll.pdb --destination_dir syzygy
INFO:root:Randomly reordering "chrome.dll"
INFO:root:Running command "('../../chrome/tools/build/win/syzygy\\../../../../..\\third_party/syzygy/binaries/exe/relink.exe', '--overwrite', '--input-image=chrome.dll', '--input-pdb=chrome.dll.pdb', '--output-image=C:\\src\\chromium3\\src\\out\\gn\\syzygy\\chrome.dll', '--output-pdb=C:\\src\\chromium3\\src\\out\\gn\\syzygy\\chrome.dll.pdb', '--seed=1347344')".
[0617/013004:INFO:application_impl.h(46)] Syzygy Relinker Version 0.8.19.0 (da2c31c).
[0617/013004:INFO:application_impl.h(48)] Copyright (c) Google Inc. All rights reserved.
[0617/013004:INFO:pe_relinker.cc(138)] Input module : C:\src\chromium3\src\out\gn\chrome.dll
[0617/013004:INFO:pe_relinker.cc(139)] Input PDB    : C:\src\chromium3\src\out\gn\chrome.dll.pdb
[0617/013004:INFO:pe_relinker.cc(140)] Output module: C:\src\chromium3\src\out\gn\syzygy\chrome.dll
[0617/013004:INFO:pe_relinker.cc(141)] Output PDB   : C:\src\chromium3\src\out\gn\syzygy\chrome.dll.pdb
[0617/013004:INFO:pe_relinker.cc(57)] Decomposing module: C:\src\chromium3\src\out\gn\chrome.dll
[0617/013013:ERROR:decomposer.cc(310)] PDB file does not contain a FIXUP stream. Module must be linked with '/PROFILE' or '/DEBUGINFO:FIXUP' flag.
[0617/013013:ERROR:pe_relinker.cc(66)] Unable to decompose module: C:\src\chromium3\src\out\gn\chrome.dll
[0617/013013:ERROR:relink_app.cc(215)] Failed to initialize relinker.
Traceback (most recent call last):
  File "../../chrome/tools/build/win/syzygy/reorder.py", line 111, in <module>
    sys.exit(main(_ParseOptions()))
  File "../../chrome/tools/build/win/syzygy/reorder.py", line 83, in main
    options.destination_dir)
  File "../../chrome/tools/build/win/syzygy/reorder.py", line 67, in _ReorderBinary
    return _Shell(*cmd)
  File "../../chrome/tools/build/win/syzygy/reorder.py", line 33, in _Shell
    raise RuntimeError('Command "%s" returned %d.' % (cmd, prog.returncode))
RuntimeError: Command "('../../chrome/tools/build/win/syzygy\\../../../../..\\third_party/syzygy/binaries/exe/relink.exe', '--overwrite', '--input-image=chrome.dll', '--input-pdb=chrome.dll.pdb', '--output-image=C:\\src\\chromium3\\src\\out\\gn\\syzygy\\chrome.dll', '--output-pdb=C:\\src\\chromium3\\src\\out\\gn\\syzygy\\chrome.dll.pdb', '--seed=1347344')" returned 1.

The args.gn settings are:

target_cpu="x86"
is_debug=false
is_component_build=false
is_official_build = true

The equivalent GYP build (GYP_DEFINES=buildtype=Official) builds without errors. This is interfering with GYP/gn build comparison tests.

Not sure how to tag so assigning to someone who can triage or suggest the fix.

Presumably the problem is that the .gn files are setup incorrectly such that official does not automatically add the /PROFILE flag.