MacViews: Don't draw custom frame on Mac

MacViews: Don't draw custom frame on Mac

We don't want to draw custom titlebar and borders on Mac.
Change BrowserFrame to delegate UseCustomFrame() to NativeBrowserFrame, and
provide appropriate overrides for the platforms:
  Mac -> false
  Win, ChromeOS -> true
  Desktop Linux -> follow user pref

Consolidate Desktop Linux specific code into DesktopBrowserFrameAuraLinux.

BUG=425229
Committed: https://crrev.com/70af3549366e24509cf05e6903a8431ba8af037b
Cr-Commit-Position: refs/heads/master@{#311600}

[Andre, 2015-01-14 22:50:49]

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

[Andre, 2015-01-14 22:50:49]

sky@ please review.

[sky, 2015-01-15 01:11:19]

LGTM

[Andre, 2015-01-15 01:12:57]

The CQ bit was checked by andresantoso@chromium.org

[commit-bot: I haz the power, 2015-01-15 01:13:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/796433003/1

[commit-bot: I haz the power, 2015-01-15 01:18:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-15 01:19:06]

Patchset 1 (id:??) landed as
https://crrev.com/70af3549366e24509cf05e6903a8431ba8af037b
Cr-Commit-Position: refs/heads/master@{#311600}