Focus behavior: Change background-color instead of font-weight

[jhrdina]

Buttons should use background-color change for focus instead of font-weight change.

Expected outcome

Button's background becomes darker on focus as mentioned in Google Design Spec and implemented in material-design-lite (their css). The font-weight is not changed (default font-weight should be 500 as mentioned in #94).

Image: material-design-lite demo, their CSS implementation here

Actual outcome

Button's font-weight changes on focus, background stays the same.

Image: paper-card demo

[abdonrd]

👍

[keanulee]

We decided to use font-weight to show focus state instead of background color because we have received feedback that background-color may not provide enough contrast for a11y. For this reason, we cannot change the font-weight in #94 because that would be too close to the focus state.

[abdonrd]

@keanulee oh! :(

Then you should change the spec of MD?