The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c94fbe298c74fd17df6691b41caa102b24f48723

commit c94fbe298c74fd17df6691b41caa102b24f48723
Author: Yuke Liao <liaoyuke@chromium.org>
Date: Thu Jul 13 18:42:47 2017

[iOS] Add extra_attributes property to create_bundle target of GN.

This CL adds extra_attributes property to create_bundle target so that
these values can be specified in BUILD files instead of hard coded in
GN.

Bug:  740800 , 709289
Change-Id: I1c0393e11405527bda5cf70fb8b653fc76454b97
Reviewed-on: https://chromium-review.googlesource.com/566390
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486448}
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/bundle_data.h
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/create_bundle_target_generator.cc
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/create_bundle_target_generator.h
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/docs/reference.md
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/functions_target.cc
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/variables.cc
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/variables.h
[modify] https://crrev.com/c94fbe298c74fd17df6691b41caa102b24f48723/tools/gn/xcode_writer.cc

Not yet fixed. There are still TODOs associated with this bug to clean up old code, and is right now blocked by the broken gn roller.