[CSS Grid Layout] Grid items must set a new formatting context.

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index 5f51066734ecbe40ef68acca735f517b9442cb21..9fbfde8267346c5a918c71293f7c3f6bcc7d7868 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -1521,7 +1521,8 @@ void RenderBlock::addVisualOverflowFromTheme()
 bool RenderBlock::createsBlockFormattingContext() const

[Julien - ping for review, 2014/11/11 16:27:01]

This function is deeply misnamed as most elements listed in it don't establish
*block* formatting contexts. Let's rename it to createNewFormattingContext for
clarity.

That would also help explain that we can have other impact from this change
(like float not protruding into the next grid item, which we should test btw).

[jfernandez, 2014/11/12 13:22:44]

Done.
Added a new layout tests for that issue.

 {
     return isInlineBlockOrInlineTable() || isFloatingOrOutOfFlowPositioned() || hasOverflowClip() || isFlexItemIncludingDeprecated()
-        || style()->specifiesColumns() || isRenderFlowThread() || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isDocumentElement() || style()->columnSpan();
+        || style()->specifiesColumns() || isRenderFlowThread() || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot()
+        || isDocumentElement() || style()->columnSpan() || containingBlock()->isRenderGrid();

[Manuel Rego, 2014/11/11 13:54:22]

It think that you could define something similar to:
RenderBox::isFlexItemIncludingDeprecated()

It might be useful in other places in the future.

[Julien - ping for review, 2014/11/11 16:27:01]

I don't have a preference about adding a helper function.

However I think we will want to use parent() instead of containingBlock() as
positioned elements create a new formatting context anyway. Also parent() is a
lot cheaper.

[jfernandez, 2014/11/12 13:22:44]

Done.

[jfernandez, 2014/11/12 13:22:44]

Done.

 }
 
 void RenderBlock::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox* child)