[LayoutNG] Shrink columns after spanner in fixed-size multicol.

We had code for this, but it depended on nested multicol to work.

Bug: 829028
Change-Id: I114c0baa394f21005b1e83619db5a577eea1f913
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944390Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720235}

third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.cc

@@ -373,9 +373,8 @@ scoped_refptr<const NGLayoutResult> NGColumnLayoutAlgorithm::LayoutRow(
   // If block-size is non-auto, subtract the space for content we've consumed in
   // previous fragments. This is necessary when we're nested inside another
   // fragmentation context.
-  if (is_constrained_by_outer_fragmentation_context_ &&
-      column_size.block_size != kIndefiniteSize) {
-    if (BreakToken())
+  if (column_size.block_size != kIndefiniteSize) {
+    if (BreakToken() && is_constrained_by_outer_fragmentation_context_)
       column_size.block_size -= BreakToken()->ConsumedBlockSize();
 
     // Subtract the space already taken in the current fragment (spanners and

third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm_test.cc

@@ -4856,6 +4856,47 @@ TEST_F(NGColumnLayoutAlgorithmTest, SpannerMarginsRtl) {
   EXPECT_EQ(expectation, dump);
 }
 
+TEST_F(NGColumnLayoutAlgorithmTest, FixedSizeMulticolWithSpanner) {
+  SetBodyInnerHTML(R"HTML(
+    <style>
+      #parent {
+        columns: 3;
+        column-gap: 10px;
+        column-fill: auto;
+        width: 320px;
+        height: 300px;
+      }
+    </style>
+    <div id="container">
+      <div id="parent">
+        <div style="width:33px; height:300px;"></div>
+        <div style="column-span:all; width:44px; height:50px;"></div>
+        <div style="width:55px; height:450px;"></div>
+      </div>
+    </div>
+  )HTML");
+
+  String dump = DumpFragmentTree(GetElementById("container"));
+  String expectation = R"DUMP(.:: LayoutNG Physical Fragment Tree ::.
+  offset:unplaced size:1000x300
+    offset:0,0 size:320x300
+      offset:0,0 size:100x100
+        offset:0,0 size:33x100
+      offset:110,0 size:100x100
+        offset:0,0 size:33x100
+      offset:220,0 size:100x100
+        offset:0,0 size:33x100
+      offset:0,100 size:44x50
+      offset:0,150 size:100x150
+        offset:0,0 size:55x150
+      offset:110,150 size:100x150
+        offset:0,0 size:55x150
+      offset:220,150 size:100x150
+        offset:0,0 size:55x150
+)DUMP";
+  EXPECT_EQ(expectation, dump);
+}
+
 TEST_F(NGColumnLayoutAlgorithmTest, BreakInsideSpannerWithMargins) {
   SetBodyInnerHTML(R"HTML(
     <style>