dialog: shift+tab doesn't loop properly after it reaches the beginning

[frkfir]

Actual Behavior:

• `What is the issue? *
  shift+tab doesn't work properly when md-dialog opens.
  Can't go to the last element/button etc.. that appear on this dialog.
  It get lost. only Tab key works has expected.
• `What is the expected behavior?
  shift+tab will work properly when md-dialog opens and get to the last ellement/button etc that appear on the dialog.
  It's supposed to behave in a circular way. (looped)

CodePen (or steps to reproduce the issue): *

• `CodePen Demo which shows your issue: N/A
• `Details:
  Happens on https://material.angularjs.org/latest/

AngularJS Versions: *

• `AngularJS Version: 1.1.5
• `AngularJS Material Version: 1.1.2 and also happens on 1.1.5

Additional Information:

• `Browser Type: * Chrome, Firefox, Explorer etc...
• `Browser Version: * Chrome Version 62.0.3202.75 (Official Build) (32-bit)
• `OS: * Windows 7
• `Stack Traces: N/A

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[EladBezalel]

@Splaktar do you mind taking a look at that?

[Splaktar]

I'm able to reproduce. It loops fine when going forward, but when going backwards it just stops at the 1st tabindex and never loops over to the last tabindex.