MacViews: Replace aura::WindowTracker with NativeWindowTracker

MacViews: Replace aura::WindowTracker with NativeWindowTracker

Using aura::WindowTracker won't compile with MacViews. Replace it
with the cross-platform NativeWindowTracker.

BUG=425229
Committed: https://crrev.com/227f4538f94e729f849881f20c7383f18e1f8a83
Cr-Commit-Position: refs/heads/master@{#319528}

[Andre, 2015-03-04 23:52:31]

andresantoso@chromium.org changed reviewers:
+ msw@chromium.org

[Andre, 2015-03-04 23:52:32]

Michael, PTAL.

[msw, 2015-03-06 19:38:55]

lgtm

[Andre, 2015-03-06 19:39:27]

The CQ bit was checked by andresantoso@chromium.org

[commit-bot: I haz the power, 2015-03-06 19:41:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/965103005/1

[commit-bot: I haz the power, 2015-03-06 21:42:50]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-06 21:42:51]

Try jobs failed on following builders:
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_TIMED_OUT, no build
URL)
Timed out jobs are not retried to avoid causing additional load on the builders
with large pending queues.

[Andre, 2015-03-06 21:45:22]

The CQ bit was checked by andresantoso@chromium.org

[commit-bot: I haz the power, 2015-03-06 21:46:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/965103005/1

[commit-bot: I haz the power, 2015-03-06 23:47:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-06 23:47:57]

Patchset 1 (id:??) landed as
https://crrev.com/227f4538f94e729f849881f20c7383f18e1f8a83
Cr-Commit-Position: refs/heads/master@{#319528}