[css-grid] Clearing override sizes before running grid's layout logic.

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 83321cd962f46af6b19bf1dffeb2538bb6e33b00..5d966a49145afaf9f920234fae4f2d77cfba834c 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1888,6 +1888,11 @@ void FrameView::layoutOrthogonalWritingModeRoots()
 {
     for (auto& root : m_orthogonalWritingModeRootList.ordered()) {
         ASSERT(root->isBox() && toLayoutBox(*root).isOrthogonalWritingModeRoot());
+        if (toLayoutBox(*root).hasContainingBlockOverrideSize() || toLayoutBox(*root).hasOverrideSize()) {

[cbiesinger, 2016/09/26 11:48:32]

Hmm, so I understand why you're doing this but I think there are two (related)
problems:
- For each layout pass, you force-layout all orthogonal roots whether they need
to be laid out or not. Shouldn't you check .needsLayout() ||
root->parent().needsLayout()?
- You lay out the child but the parent may not be marked for layout. That means
that there may not be a full grid layout to lay out the child at the correct
size, and the child may remain at the incorrect size! (The size without the
override applied)

[jfernandez, 2016/09/26 13:38:02]

For the case I'm trying to solve is not enough to check for needsLayout, since
this
re-layout is triggered by scrollbar changes which set grid container's preferred
width
as dirty; grid container will be marked for layout later.
Yeah, as I said, for the scenario I'm trying to solve the container will be
marked
for layout, but it's true that this may not be the case in other situations.
I'll have to
think about it.

+            toLayoutBox(*root).clearOverrideSize();
+            toLayoutBox(*root).clearContainingBlockOverrideSize();
+            root->setNeedsLayout(LayoutInvalidationReason::SizeChanged);
+        }
         if (!root->needsLayout()
             || root->isOutOfFlowPositioned()
             || root->isColumnSpanAll()