Menu does not focus if first item is disabled and is not focusable for keyboard (a11y).

[rgthree]

Actual Behavior:

• What is the issue? * When opening a menu list whose first item is disabled, the menu does not focus. This results in the menu not being usable with only a keyboard as arrows/tabs move around behind the menu.
• What is the expected behavior? The menu would focus the first item that can be focused and works as expected otherwise.

CodePen (or steps to reproduce the issue): *

• CodePen Demo which shows your issue: http://codepen.io/rgthree/pen/dOyaVj
• Details: In the demo

Angular Versions: *

• Angular Version: 1.5.5/angular.js, 1.5.5/angular-aria.js, 1.5.5/angular-animate.js
• Angular Material Version: 1.1.0/angular-material.min.js

Additional Information:

• Browser Type: * Chrome
• Browser Version: * 56.0.2902.0 (Official Build) dev (64-bit)
• OS: * Linux
• Stack Traces:

[clshortfuse]

Good news! We have already fixed this in the master branch with this PR: #9228