[css-grid] Preemptively store intrinsic sizes during layout

third_party/WebKit/Source/core/layout/LayoutGrid.cpp

Index: third_party/WebKit/Source/core/layout/LayoutGrid.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
index 00436b95c574ea8221b85725c835a36ec99822cc..eb9934f3ef736831056c3d4eb5da7a48cdc0befd 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -280,6 +280,21 @@ void LayoutGrid::UpdateBlockLayout(bool relayout_children) {
     // resolve heights properly (like for positioned items for example).
     ComputeTrackSizesForDefiniteSize(kForColumns, available_space_for_columns);
 
+    // We take the chance to store the intrinsic sizes as the track sizing
+    // algorithm always compute them as part of its execution. Apart from saving

[jfernandez, 2017/04/21 14:48:02]

What do you mean with this sentence ?

[svillar, 2017/04/21 14:51:24]

In order to compute the intrinsic sizes we have to call the track sizing
algorithm. The algorithm always computes the intrinsic sizes because it's just
an intermediate result of its execution, is not avoidable and it does not
require any extra work.

+    // an algorithm execution, it fixes the use case of computing the preferred

[jfernandez, 2017/04/21 14:48:02]

Why we save an algorithm execution with this change ?

[svillar, 2017/04/21 14:51:23]

Because we wouldn't have to call the algorithm later if
minPreferredLogicalWidth() is called because they'd be already computed. I can
rephrase it if you want.

+    // logical widths *after* the layout process. Although not very common, this
+    // happens in the Mac (content::RenderViewImpl::didUpdateLayout()) or under
+    // some circumstances when grids are also flex items (crbug.com/708159).
+    if (PreferredLogicalWidthsDirty()) {
+      LayoutUnit scrollbar_width = LayoutUnit(ScrollbarLogicalWidth());
+      min_preferred_logical_width_ =
+          track_sizing_algorithm_.MinContentSize() + scrollbar_width;
+      max_preferred_logical_width_ =
+          track_sizing_algorithm_.MaxContentSize() + scrollbar_width;
+      ClearPreferredLogicalWidthsDirty();
+    }
+
     // 2- Next, the track sizing algorithm resolves the sizes of the grid rows,
     // using the grid column sizes calculated in the previous step.
     if (CachedHasDefiniteLogicalHeight()) {