Implement grid/flex layout for ( bug 1230207).CSS Box Alignment currently applies only to CSS Flexbox and CSS Grid. Implement full support for CSS Box Alignment for CSS Grid, support the missing values: start, end, self-start, self-end, left, right, last-baseline, space-evenly( bug 1176782).The related feature display: contents has been supported since Firefox 37.Resolved value of grid-template-columns,grid-template-rows in px units ( bug 978212).align-content and justify-content are now supported on grid layouts ( bug 1151214).align-self and justify-self are now supported on grid layouts ( bug 1151213).The implied minimum size of grid Items, that is the special min-width and min-height auto behavior has been implemented ( bug 1176775).Gutters, that is the grid-column-gap, grid-row-gap, and grid-gap properties are now supported ( bug 1176792).Our implementation of CSS Grids has been improved and is no more considered experimental it is now activated by default in nightly and developer edition, but not for beta and release ( bug 1000592):.word-spacing now allows percentage values ( bug 1038663).

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