Update AuraWindowRegistry to create only positive window IDs.

Update AuraWindowRegistry to create only positive window IDs.

Previously AuraWindowRegistry was allocating ID 0 to first window. This
breaks assumptions made in other places, e.g. DCHECK in
DesktopMediaPickerDialogView. After this change the implementation
guarantees that window IDs are always unique positive integers.

Committed: https://crrev.com/fc74c509cd0575563483e5f6b1bd5fd930754bd5
Cr-Commit-Position: refs/heads/master@{#291708}

[jam, 2014-08-25 02:06:28]

lgtm

[Sergey Ulanov, 2014-08-25 16:37:43]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2014-08-25 16:38:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sergeyu@chromium.org/499813002/60001

[commit-bot: I haz the power, 2014-08-25 17:46:28]

Committed patchset #1 (60001) as 3d1f35cecc24b6c6d0ef0826edcad70312d7d859

[commit-bot: I haz the power, 2014-09-10 02:35:27]

Patchset 1 (id:??) landed as
https://crrev.com/fc74c509cd0575563483e5f6b1bd5fd930754bd5
Cr-Commit-Position: refs/heads/master@{#291708}