Add issue to color-stops about swapping steps 2 and 3 of the location fixup, so we can do interpolation purely at computed-value time.

Author: tabatkins

css4-images/Overview.html

@@ -2329,6 +2329,13 @@ <h3 id=color-stop-syntax><span class=secno>5.5. </span> Gradient
     with positions.
   </ol>
 
+  <p class=issue> This requires us to wait until <em>after</em> layout to do
+   fix-up, because implied-position stops (set by step 3) may depend on stops
+   that need layout information to place, and which may be corrected by step
+   2. Swapping steps 2 and 3 would let us interpolate color-stops purely at
+   computed-value time, which is a nice plus, at the cost of changing
+   behavior from level 3 for some edge cases that triggered fixup.
+
   <p> If multiple color-stops have the same position, they produce an
    infinitesimal transition from the one specified first in the rule to the
    one specified last. In effect, the color suddenly changes at that position

css4-images/Overview.src.html

@@ -1894,6 +1894,15 @@ <h3 id='color-stop-syntax'>
 			set their positions so that they are evenly spaced between the preceding and following color-stops with positions.
 	</ol>
 
+	<p class='issue'>
+		This requires us to wait until <em>after</em> layout to do fix-up,
+		because implied-position stops (set by step 3)
+		may depend on stops that need layout information to place,
+		and which may be corrected by step 2.
+		Swapping steps 2 and 3 would let us interpolate color-stops purely at computed-value time,
+		which is a nice plus,
+		at the cost of changing behavior from level 3 for some edge cases that triggered fixup.
+
 	<p>
 		If multiple color-stops have the same position, 
 		they produce an infinitesimal transition from the one specified first in the rule