Revert of Mandoline: Remove native_viewport.mojom

Revert of Mandoline: Remove native_viewport.mojom (patchset #14 id:250001 of https://codereview.chromium.org/1149083010/)

Reason for revert:
This patch seems to break GN bots on Windows. See e.g. http://build.chromium.org/p/chromium.win/builders/Win8%20GN/builds/8167

Original issue's description:
> Mandoline: Remove native_viewport.mojom
>
> native_viewport mojom + app add a lot of unnecessary complexity. For now, this should be a part of the view_manager. A future patch will get rid of native_viewport completely and will teach display_manager to dispense platform_windows.
>
> BUG=487881
> Test=internal change only.
>
> Committed: https://crrev.com/3a4eab3f2f4fd8f7c7eb4d195c0e86a47e085d98
> Cr-Commit-Position: refs/heads/master@{#333183}

TBR=sky@chromium.org,fsamuel@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=487881
Committed: https://crrev.com/57d15367b02b9123792a5c2193185983476a3762
Cr-Commit-Position: refs/heads/master@{#333245}

[henrika (OOO until Aug 14), 2015-06-08 06:56:43]

Created Revert of Mandoline: Remove native_viewport.mojom

[commit-bot: I haz the power, 2015-06-08 06:56:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1164553004/1

[commit-bot: I haz the power, 2015-06-08 06:57:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-08 06:58:26]

Patchset 1 (id:??) landed as
https://crrev.com/57d15367b02b9123792a5c2193185983476a3762
Cr-Commit-Position: refs/heads/master@{#333245}