[css-grid] Import W3C Test Suite

third_party/WebKit/LayoutTests/external/csswg-test/css-grid-1/README.md

+CSS Grid Layout Module Level 1 Test Suite
+-----------------------------------------
+
+Directory containing the CSS Grid Layout spec test suite.
+
+This suite is structured in different folders for each section of the spec
+(the name of the folders corresponds to the "id" of each section):
+
+* [3 Grid Containers](https://drafts.csswg.org/css-grid-1/#grid-model):
+  `grid-model`
+* [4 Grid Items](https://drafts.csswg.org/css-grid-1/#grid-items):
+  `grid-items`
+* [5 The Explicit Grid](https://drafts.csswg.org/css-grid-1/#grid-definition):
+  `grid-definition`
+* [6 The Implicit Grid](https://drafts.csswg.org/css-grid-1/#implicit-grids):
+  `implicit-grids`
+* [7 Grid Definition Shorthand](https://drafts.csswg.org/css-grid-1/#grid-shorthand):
+  `grid-shorthand`
+* [8 Clamping Overlarge Grids](https://drafts.csswg.org/css-grid-1/#overlarge-grids):
+  `overlarge-grids`
+* [9 Placing Grid Items](https://drafts.csswg.org/css-grid-1/#placement):
+  `placement`
+* [10 Absolute Positioning](https://drafts.csswg.org/css-grid-1/#abspos):
+  `abspos`
+* [11 Alignment and Spacing](https://drafts.csswg.org/css-grid-1/#alignment):
+  `alignment`
+* [12 Grid Sizing](https://drafts.csswg.org/css-grid-1/#layout-algorithm):
+  `layout-algorithm`
+* [13 Fragmenting Grid Layout](https://drafts.csswg.org/css-grid-1/#pagination):
+  `pagination`
+
+Links:
+
+* [Spec Editor's Draft](https://drafts.csswg.org/css-grid-1/)
+* [Test Plan](http://test.csswg.org/source/css-grid-1/test-plan/)
+* [Test Suite](http://test.csswg.org/suites/css-grid-1_dev/nightly-unstable/)