Update the GN reference.md documentation.

Update the GN reference.md documentation.

TBR=dpranke@chromium.org

Review-Url: https://codereview.chromium.org/2656873002
Cr-Commit-Position: refs/heads/master@{#446110}
Committed: https://chromium.googlesource.com/chromium/src/+/8598442a712230a26347c7adcfc95cbb8e95a46f

[brettw, 2017-01-25 20:36:22]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2017-01-25 20:36:50]

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

[commit-bot: I haz the power, 2017-01-25 20:45:44]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1485376582389470, "parent_rev":
"75356d0ffb30d91be77d3d953a879490f4207194", "commit_rev":
"8598442a712230a26347c7adcfc95cbb8e95a46f"}

[commit-bot: I haz the power, 2017-01-25 20:46:16]

Description was changed from

==========
Update the GN reference.md documentation.

TBR=dpranke@chromium.org
==========

to

==========
Update the GN reference.md documentation.

TBR=dpranke@chromium.org

Review-Url: https://codereview.chromium.org/2656873002
Cr-Commit-Position: refs/heads/master@{#446110}
Committed:
https://chromium.googlesource.com/chromium/src/+/8598442a712230a26347c7adcfc9...
==========

[commit-bot: I haz the power, 2017-01-25 20:46:17]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/8598442a712230a26347c7adcfc9...

[Dirk Pranke, 2017-01-25 21:39:40]

Aww, you remembered :). LGTM.