Mark build arguments implicitly used in GN.

Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a revert of the GN roll. The particular issue is that a build argument in a BUILD.gn file was used in only one of the toolchains, so the other toolchains were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used, and anything in a .gni file is the same. The remaining cases are pretty confusing so it seems better to not warn in this case instead of requiring the author to wrap the build variable in a condition based on the usage.

TBR=dpranke

Committed: https://crrev.com/8b05f575431f4854163470695cf1a6f6495263ce
Cr-Commit-Position: refs/heads/master@{#405291}

[brettw, 2016-07-13 20:11:55]

brettw@chromium.org changed reviewers:
+ dpranke@chromium.org

[brettw, 2016-07-13 20:12:01]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-13 20:13:12]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[brettw, 2016-07-13 20:33:16]

Description was changed from

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.
==========

to

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.

TBR=dpranke
==========

[brettw, 2016-07-13 20:33:37]

I'm TBRing this since it blocks a GN roll I want to re-land.

[brettw, 2016-07-13 20:33:46]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2016-07-13 20:33:52]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2016-07-13 20:34:10]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Dirk Pranke, 2016-07-13 21:20:27]

lgtm

[commit-bot: I haz the power, 2016-07-13 21:29:39]

Description was changed from

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.

TBR=dpranke
==========

to

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.

TBR=dpranke
==========

[commit-bot: I haz the power, 2016-07-13 21:29:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-13 21:29:42]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-13 21:32:39]

Description was changed from

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.

TBR=dpranke
==========

to

==========
Mark build arguments implicitly used in GN.

This regressed in https://codereview.chromium.org/2092623002 which caused a
revert of the GN roll. The particular issue is that a build argument in a
BUILD.gn file was used in only one of the toolchains, so the other toolchains
were giving unused variable errors on it.

Build variables kept at their default values already are marked implicitly used,
and anything in a .gni file is the same. The remaining cases are pretty
confusing so it seems better to not warn in this case instead of requiring the
author to wrap the build variable in a condition based on the usage.

TBR=dpranke

Committed: https://crrev.com/8b05f575431f4854163470695cf1a6f6495263ce
Cr-Commit-Position: refs/heads/master@{#405291}
==========

[commit-bot: I haz the power, 2016-07-13 21:32:40]

Patchset 1 (id:??) landed as
https://crrev.com/8b05f575431f4854163470695cf1a6f6495263ce
Cr-Commit-Position: refs/heads/master@{#405291}