[css-transforms-2] Add 'none' value to the individual transforms. Fixes w3c#244.

Author: tabatkins

css-transforms-2/Overview.bs

@@ -37,8 +37,8 @@ Fluff here.
 
 <pre class="propdef">
 Name: translate
-Value: <<length-percentage>> [ <<length-percentage>> <<length>>? ]?
-Initial: 0
+Value: none | <<length-percentage>> [ <<length-percentage>> <<length>>? ]?
+Initial: none
 Inherited: no
 Percentages: relative to the width of the containing block (for the first value) or the height (for the second value)
 Media: visual
@@ -48,17 +48,17 @@ Animatable: as <<length>> or <<percentage>> list
 
 <pre class="propdef">
 Name: rotate
-Value: <<number>>{3}? <<angle>>
-Initial: 0deg
+Value: none | <<number>>{3}? <<angle>>
+Initial: none
 Inherited: no
 Media: visual
 Animatable: as SLERP
 </pre>
 
 <pre class="propdef">
 Name: scale
-Value: <<number>>{1,3}
-Initial: 1
+Value: none | <<number>>{1,3}
+Initial: none
 Inherited: no
 Media: visual
 Animatable: as <<number>> list
@@ -88,6 +88,17 @@ each specifying a scale along one axis,
 in order X, Y, then Z.
 Unspecified scales default to ''1''.
 
+All three properties accept
+(and default to)
+the value <dfn value for="translate, rotate, scale">none</dfn>,
+which produces no transform at all.
+In particular,
+this value does <em>not</em> trigger the creation of a stacking context,
+while all other values
+(including identity transforms like ''translate: 0px'')
+create a stacking context,
+per usual for transforms.
+
 
 Current Transformation Matrix {#ctm}
 ====================================