layout: Freeze flex item properly

Fix the currently logic that a item will freeze if it should
grow(shrink) and its basesize is less(more) than its min(max) size. Also
fix the divide by zero error when an item should shrink but it has zero
length and zero min size.

components/layout/flex.rs

@@ -276,9 +276,8 @@ impl FlexLine {
         // https://drafts.csswg.org/css-flexbox/#resolve-flexible-lengths
         for item in items.iter_mut().filter(|i| !(i.is_strut && collapse)) {
             item.main_size = max(item.min_size, min(item.base_size, item.max_size));
-            if item.main_size != item.base_size
-                || (self.free_space > Au(0) && item.flex_grow == 0.0)
-                || (self.free_space < Au(0) && item.flex_shrink == 0.0) {
+            if (self.free_space > Au(0) && (item.flex_grow == 0.0 || item.base_size >= item.max_size)) ||
+                (self.free_space < Au(0) && (item.flex_shrink == 0.0 || item.base_size <= item.min_size)) {
                     item.is_frozen = true;
                 } else {
                     item.is_frozen = false;
@@ -311,7 +310,7 @@ impl FlexLine {
                     (item.flex_shrink * item.base_size.0 as f32 / total_scaled, item.min_size)
                 };
                 let variation = self.free_space.scale_by(factor);
-                if variation.0.abs() > (end_size - item.main_size).0.abs() {
+                if variation.0.abs() >= (end_size - item.main_size).0.abs() {
                     // Use constraint as the target main size, and freeze item.
                     total_variation += end_size - item.main_size;
                     item.main_size = end_size;

tests/wpt/metadata-css/css-flexbox-1_dev/html/flexbox_computedstyle_min-width-auto.htm.ini

@@ -1,4 +1,5 @@
 [flexbox_computedstyle_min-width-auto.htm]
   type: testharness
-  expected: TIMEOUT
+  [flexbox | computed style | min-width: auto]
+    expected: FAIL