change keyword normal to auto per #2660

Per suggestion and reasoning in issue #2660, change keyword normal to auto.

Author: tantek

css-scrollbars-1/Overview.bs

@@ -64,10 +64,10 @@ Name: scrollbar-3dlight-color,
       scrollbar-highlight-color, 
       scrollbar-track-color, 
       scrollbar-shadow-color
-Value: normal | <<color>>
-Initial: normal
+Value: auto | <<color>>
+Initial: auto
 Inherited: yes
-Computed value: the computed color or the keyword normal
+Computed value: the computed color or the keyword auto
 Animation type: <a href="https://www.w3.org/TR/css3-transitions/#animtype-color">color</a>
 Applies to: block containers and boxes that establish a formatting context [same as elements that <a href=https://www.w3.org/TR/CSS22/visufx.html#propdef-overflow">'overflow' applies to</a>]
 Percentages: n/a
@@ -88,7 +88,7 @@ Note: Unlike 'overflow' (and overflow-*) properties,
 scrollbar-* values set on the HTML body element are not propagated to viewport.
 
 <dl dfn-type="value" dfn-for="scrollbar-base-color">
-<dt><dfn>normal</dfn>
+<dt><dfn>auto</dfn>
 <dd>default platform rendering for that portion of the scrollbar, in the absence of any other 
 related scrollbar color properties. See details below for which scrollbar color are related to which.
 <dt><dfn><<color>></dfn>
@@ -97,17 +97,17 @@ related scrollbar color properties. See details below for which scrollbar color
 
 Details:
 
-If scrollbar-track-color computes to normal, and scrollbar-face-color and scrollbar-highlight-color are not normal, 
+If scrollbar-track-color computes to auto, and scrollbar-face-color and scrollbar-highlight-color are not auto, 
 they are combined (e.g. dithered) to color the scrollbar track. 
-If just one of scrollbar-face-color and scrollbar-highlight-color is not normal, it is used to color the scrollbar track. 
+If just one of scrollbar-face-color and scrollbar-highlight-color is not auto, it is used to color the scrollbar track. 
 
-If scrollbar-face-color computes to normal and scrollbar-base-color is not normal, 
+If scrollbar-face-color computes to auto and scrollbar-base-color is not auto, 
 then use its value for scrollbar-face-color.
 
-If scrollbar-3dlight-color computes to normal and scrollbar-base-color is not normal, 
+If scrollbar-3dlight-color computes to auto and scrollbar-base-color is not auto, 
 then use its value for scrollbar-3dlight-color.
 
-If an element has both horizontal and vertical scrollbars, and the scrollbar-face-color is not normal, 
+If an element has both horizontal and vertical scrollbars, and the scrollbar-face-color is not auto, 
 use it for the area in the corner between the two scrollbars.
 
 If the color of any part of the scrollbar is specified,