Devtools[LayoutEditor]: Always show medias in selector tooltip

Devtools[LayoutEditor]: Always show medias in selector tooltip

As a driveby: don't allow negative margin.

BUG=501896
Committed: https://crrev.com/15297eb2e99a7954fd85375eb2dee57209999858
Cr-Commit-Position: refs/heads/master@{#351648}

[sergeyv, 2015-09-29 22:17:52]

sergeyv@chromium.org changed reviewers:
+ dgozman@chromium.org

[dgozman, 2015-09-29 22:59:32]

Why would we disallow negative margin?

[pbakaus, 2015-09-30 15:11:22]

On 2015/09/29 at 22:59:32, dgozman wrote:
> Why would we disallow negative margin?

It's very hard to create a UX that works for negative margin. Thus, let's not
support them in V1.

However, we should fail gracefully, i.e. gray out the handle, show the negative
value on hover, and show a tooltip that says "Negative margins are not supported
at this time." or something.

[dgozman, 2015-09-30 19:16:11]

lgtm

[dgozman, 2015-09-30 19:16:13]

lgtm

lgtm

[sergeyv, 2015-09-30 19:52:55]

The CQ bit was checked by sergeyv@chromium.org

[commit-bot: I haz the power, 2015-09-30 19:54:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1372963006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1372963006/1

[commit-bot: I haz the power, 2015-09-30 21:40:43]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-30 21:42:26]

Patchset 1 (id:??) landed as
https://crrev.com/15297eb2e99a7954fd85375eb2dee57209999858
Cr-Commit-Position: refs/heads/master@{#351648}