Cleanup: Include the associated header file before other includes.

Cleanup: Include the associated header file before other includes.

Found by Facebook's flint tool:
$ flint ui/gfx/x/x11_error_tracker.cc
ui/gfx/x/x11_error_tracker.cc:6: The associated header file of .cpp
files should be included before any other includes.

Then built with:
$ gn gen out-gn
$ ninja -C out-gn x

BUG=None
TEST=see above
R=sadrul@chromium.org

Committed: https://crrev.com/caba47dad115e69d7f78d15bc3510de6e508eb75
Cr-Commit-Position: refs/heads/master@{#318757}

[sadrul, 2015-03-02 16:55:08]

lgtm

[tfarina, 2015-03-02 19:38:32]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-03-02 19:40:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/966173002/1

[commit-bot: I haz the power, 2015-03-02 21:09:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-02 21:10:43]

Patchset 1 (id:??) landed as
https://crrev.com/caba47dad115e69d7f78d15bc3510de6e508eb75
Cr-Commit-Position: refs/heads/master@{#318757}