Fix a cursor:-moz-initial assertion and include it in the mochitests. b=379951 r+sr=dbaron

layout/style/nsRuleNode.cpp

@@ -2493,6 +2493,9 @@ nsRuleNode::ComputeUserInterfaceData(nsStyleStruct* aStartStruct,
       ui->mCursor = parentUI->mCursor;
       ui->CopyCursorArrayFrom(*parentUI);
     }
+    else if (eCSSUnit_Initial == list->mValue.GetUnit()) {
+      ui->mCursor = NS_STYLE_CURSOR_AUTO;
+    }
     else {
       // The parser will never create a list that is *all* URL values --
       // that's invalid.

layout/style/test/test_initial_computation.html

@@ -125,7 +125,6 @@ var gBrokenInitial = {
   "bottom": true,
   "caption-side": true,
   "clear": true,
-  "cursor": true,
   "direction": true,
   "display": true,
   "empty-cells": true,