[css-overflow-3] Flow relative overflow properties

Closes #2000

Author: frivoal

css-overflow-3/Overview.bs

@@ -454,6 +454,27 @@ Overflow Viewport Propagation</h3>
 	If ''overflow/visible'' is applied to the viewport,
 	it must be interpreted as ''overflow/auto''.
 
+<h3 id=logical>
+Flow relative properties: the 'overflow-block' and 'overflow-inline' properties</h3>
+
+The following properties are processed according to the same processing model
+as the Flow-Relative box model properties defined in [[css-logical-1#box]].
+
+  <pre class="propdef">
+  Name: overflow-inline, overflow-block
+  Value: <<'overflow'>>
+  Initial: auto
+  Applies to: Same as 'overflow-x' and 'overflow-y'
+  Inherited: No
+  Percentages: N/A
+  Media: visual
+  Computed value: Same as 'overflow-x' and 'overflow-y'
+  </pre>
+
+  These properties correspond to the
+  'overflow-x' and 'overflow-y' properties.
+  The mapping depends on the element's 'writing-mode'.
+
 <h2 id="max-lines">
 Limiting Visible Lines: the 'max-lines' property</h2>