[css-values-4] Further tweaks of math-function simplification, ensuring that old-style calc()s will fully simplify down to a sum of values.

Author: tabatkins

css-values-4/Overview.bs

@@ -3432,7 +3432,11 @@ Simplification</h4>
 
 		6. If |root| is a Sum node:
 
-			1. For each set of |root|'s children
+			1. For each of |root|'s children
+				that are Sum nodes,
+				replace them with their children.
+
+			2. For each set of |root|'s children
 				that are numeric values with identical units,
 				remove those children
 				and replace them with a single numeric value
@@ -3442,18 +3446,30 @@ Simplification</h4>
 				(E.g. combine numbers, combine percentages,
 				combine px values, etc.)
 
-			2. If |root| has only a single child at this point,
+			3. If |root| has only a single child at this point,
 				return the child.
 				Otherwise, return |root|.
 
 		7. If |root| is a Product node:
 
-			1. If |root| has multiple children that are numbers
+			1. For each of |root|'s children
+				that are Product nodes,
+				replace them with their children.
+
+			2. If |root| has multiple children that are numbers
 				(not percentages or dimensions),
 				remove them and replace them with a single number
 				containing the product of the removed nodes.
 
-			2. If |root| contains only numeric values
+			3. If |root| contains only two children,
+				one of which is a number
+				(not a percentage or dimension)
+				and the other of which is a Sum
+				whose children are all numeric values,
+				multiply all of the Sum's children by the number,
+				then return the Sum.
+
+			4. If |root| contains only numeric values
 				and/or Invert nodes containing numeric values,
 				and [=multiply two types|multiplying the types=]
 				of all the children
@@ -3466,7 +3482,7 @@ Simplification</h4>
 				is the reciprocal of its child's value),
 				expressed in the result's [=canonical unit=].
 
-			3. Return |root|.
+			5. Return |root|.
 	</div>
 
 <h3 id='calc-computed-value'>