mdTabs: with inner content, first swipe fails

[PaulMougel]

In an <md-tabs> with inner tab content, the first swipe to change tabs doesn't work. However, if we click on another tab, and then try to swipe, it works.

I was able to pinpoint the bug to 3ee83a6.

Here is the stacktrace:

Maybe #1257 will fix this bug, but it would be nice to check anyway…