docs/flag_ownership.md - experimental/chromium/src - Git at Google

 # Chrome Flag Ownership

 ellyjones@ / avi@

 [TOC]

 ## TL;DR / What Do I Need To Do?

 Look through
 [`chrome/browser/flag-metadata.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-metadata.json?sq=package:chromium&q=flag-metadata.json&g=0&l=1)
 for flags that your team added, maintains, or cares about. For each such flag
 you find, either:

 - **If it is still in use:** add entries to the owners list (see the comment at
   the top of the file) and set an appropriate expiration milestone;

 - **If it is not in use:** delete it from `kFeatureEntries` in
   [`chrome/browser/about_flags.cc`](https://cs.chromium.org/chromium/src/chrome/browser/about_flags.cc?sq=package:chromium&g=0&l=1319) or
   [`ios/chrome/browser/about_flags.mm`](https://cs.chromium.org/chromium/src/ios/chrome/browser/about_flags.mm) for iOS.
   Remember to file a cleanup bug to remove code paths that become dead. It is
   not necessary to delete the corresponding entry in `flag-metadata.json` as it
   will be cleaned up for you in the future.

 ## Wait, What Are You Doing?

 Presently, Chrome has approximately 600 entries in `chrome://flags`, many of
 which are obsolete and unused, but each of which represents configuration
 surface that is exposed to users and to QA. Worse, obsolete flags often prevent
 removal of legacy code paths that are not used in the field but are still
 reachable via a flag setting.

 To deal with that, we are moving Chrome towards a model where `chrome://flags`
 entries are what they were originally intended to be: temporary, experimental
 options. Each flag must have a set owner who can keep track of whether or when
 that flag should expire and an express time by which it will expire, either
 because the feature it controls will have become default-enabled or because the
 feature it controls will have been cancelled.

 Note that this change only affects `chrome://flags` entries, not features
 controlled via
 [`FeatureList`](https://cs.chromium.org/chromium/src/base/feature_list.h?q=FeatureList&sq=package:chromium&g=0&l=92)
 (commonly used to run Finch trials) or command-line switches.

 ## I Don't Want My Flag To Expire!

 Some flags do not control UI features, but rather are commonly-used debugging
 controls, such as `ignore-gpu-blocklist`. For these flags, see the instructions
 at the head of `flag-metadata.json`. Please be very judicious about
 never-expiring flags, since they represent ongoing engineering, test and support
 burden. The flags team will probably only approve your non-expiring flag if:

 - You regularly ask users or developers to change its value for
   debugging/support purposes
 - You have been doing so for at least six months
 - You don't plan to stop doing so any time soon

 If you have a non-expiring flag, the flags team requires a comment in the json
 file as to the rationale that it be non-expiring. A quick sentence or two will
 be fine. Yes, we are aware that, technically, JSON files can't have comments.
 Don't worry about it. You'll also need to add your flag to the permitted list in
 [`chrome/browser/flag-never-expire-list.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-never-expire-list.json?sq=package:chromium&q=flag-never-expire-list.json&g=0&l=1)
 which will require approval from the flags team.

 ## What Should My Expiry Be?

 A good rule of thumb is that your flag should expire one milestone after you
 expect your feature to have launched to stable. In other words, if your feature
 will be 100% enabled on Stable in M74, your flag should be marked as expiring in
 M75.

 Please do not stress about the expiration date. The purpose of the expiration
 milestone is to let us remove *abandoned* flags. Pick a reasonable milestone by
 which you'll be done with the flag; you can always adjust it later if your
 schedule changes.

 ## I Have Other Questions

 Please get in touch with
 [`flags-dev@chromium.org`](https://groups.google.com/a/chromium.org/forum/#!forum/flags-dev).
 If you feel like you need to have a Google-internal discussion for some reason,
 there's also
 [`chrome-flags@`](https://groups.google.com/a/google.com/forum/#!forum/chrome-flags).
	# Chrome Flag Ownership

	ellyjones@ / avi@

	[TOC]

	## TL;DR / What Do I Need To Do?

	Look through
	[`chrome/browser/flag-metadata.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-metadata.json?sq=package:chromium&q=flag-metadata.json&g=0&l=1)
	for flags that your team added, maintains, or cares about. For each such flag
	you find, either:

	- If it is still in use: add entries to the owners list (see the comment at
	the top of the file) and set an appropriate expiration milestone;

	- If it is not in use: delete it from `kFeatureEntries` in
	[`chrome/browser/about_flags.cc`](https://cs.chromium.org/chromium/src/chrome/browser/about_flags.cc?sq=package:chromium&g=0&l=1319) or
	[`ios/chrome/browser/about_flags.mm`](https://cs.chromium.org/chromium/src/ios/chrome/browser/about_flags.mm) for iOS.
	Remember to file a cleanup bug to remove code paths that become dead. It is
	not necessary to delete the corresponding entry in `flag-metadata.json` as it
	will be cleaned up for you in the future.

	## Wait, What Are You Doing?

	Presently, Chrome has approximately 600 entries in `chrome://flags`, many of
	which are obsolete and unused, but each of which represents configuration
	surface that is exposed to users and to QA. Worse, obsolete flags often prevent
	removal of legacy code paths that are not used in the field but are still
	reachable via a flag setting.

	To deal with that, we are moving Chrome towards a model where `chrome://flags`
	entries are what they were originally intended to be: temporary, experimental
	options. Each flag must have a set owner who can keep track of whether or when
	that flag should expire and an express time by which it will expire, either
	because the feature it controls will have become default-enabled or because the
	feature it controls will have been cancelled.

	Note that this change only affects `chrome://flags` entries, not features
	controlled via
	[`FeatureList`](https://cs.chromium.org/chromium/src/base/feature_list.h?q=FeatureList&sq=package:chromium&g=0&l=92)
	(commonly used to run Finch trials) or command-line switches.

	## I Don't Want My Flag To Expire!

	Some flags do not control UI features, but rather are commonly-used debugging
	controls, such as `ignore-gpu-blocklist`. For these flags, see the instructions
	at the head of `flag-metadata.json`. Please be very judicious about
	never-expiring flags, since they represent ongoing engineering, test and support
	burden. The flags team will probably only approve your non-expiring flag if:

	- You regularly ask users or developers to change its value for
	debugging/support purposes
	- You have been doing so for at least six months
	- You don't plan to stop doing so any time soon

	If you have a non-expiring flag, the flags team requires a comment in the json
	file as to the rationale that it be non-expiring. A quick sentence or two will
	be fine. Yes, we are aware that, technically, JSON files can't have comments.
	Don't worry about it. You'll also need to add your flag to the permitted list in
	[`chrome/browser/flag-never-expire-list.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-never-expire-list.json?sq=package:chromium&q=flag-never-expire-list.json&g=0&l=1)
	which will require approval from the flags team.

	## What Should My Expiry Be?

	A good rule of thumb is that your flag should expire one milestone after you
	expect your feature to have launched to stable. In other words, if your feature
	will be 100% enabled on Stable in M74, your flag should be marked as expiring in
	M75.

	Please do not stress about the expiration date. The purpose of the expiration
	milestone is to let us remove abandoned flags. Pick a reasonable milestone by
	which you'll be done with the flag; you can always adjust it later if your
	schedule changes.

	## I Have Other Questions

	Please get in touch with
	[`flags-dev@chromium.org`](https://groups.google.com/a/chromium.org/forum/#!forum/flags-dev).
	If you feel like you need to have a Google-internal discussion for some reason,
	there's also
	[`chrome-flags@`](https://groups.google.com/a/google.com/forum/#!forum/chrome-flags).