Add grid/flex layout support for <fieldset>

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

Index: third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
index e5e961f6337e716db069190cfd719b37b6136b1d..fb1610de0b6fbc6394d2fd4fc8a9ced1ab2b76ab 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
@@ -1163,9 +1163,6 @@ void LayoutBlockFlow::layoutBlockChildren(bool relayoutChildren, SubtreeLayoutSc
     BlockChildrenLayoutInfo layoutInfo(this, beforeEdge, afterEdge);
     MarginInfo& marginInfo = layoutInfo.marginInfo();
 
-    // Fieldsets need to find their legend and position it inside the border of the object.
-    // The legend then gets skipped during normal layout. The same is true for ruby text.
-    // It doesn't get included in the normal layout process but is instead skipped.
     LayoutObject* childToExclude = layoutSpecialExcludedChild(relayoutChildren, layoutScope);
 
     LayoutBox* next = firstChildBox();
@@ -1178,7 +1175,7 @@ void LayoutBlockFlow::layoutBlockChildren(bool relayoutChildren, SubtreeLayoutSc
         child->setMayNeedPaintInvalidation();
 
         if (childToExclude == child)
-            continue; // Skip this child, since it will be positioned by the specialized subclass (fieldsets and ruby runs).
+            continue; // Skip this child, since it will be positioned by the specialized subclass (ruby runs).
 
         updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, *child);
 
@@ -2410,7 +2407,7 @@ void LayoutBlockFlow::addChild(LayoutObject* newChild, LayoutObject* beforeChild
     // that isn't sufficient for us, and can only cause trouble at this point.
     LayoutBox::addChild(newChild, beforeChild);
 
-    if (madeBoxesNonInline && parent() && isAnonymousBlock() && parent()->isLayoutBlock()) {
+    if (madeBoxesNonInline && parent() && isAnonymousBlock() && parent()->isLayoutBlock() && !parent()->createsAnonymousWrapper()) {
         toLayoutBlock(parent())->removeLeftoverAnonymousBlock(this);
         // |this| may be dead now.
     }
@@ -3488,11 +3485,6 @@ void LayoutBlockFlow::createOrDestroyMultiColumnFlowThreadIfNeeded(const Compute
     if (isRuby())
         return;
 
-    // Fieldsets look for a legend special child (layoutSpecialExcludedChild()). We currently only
-    // support one special child per layout object, and the flow thread would make for a second one.
-    if (isFieldset())
-        return;
-
     // Form controls are replaced content, and are therefore not supposed to support multicol.
     if (isFileUploadControl() || isTextControl() || isListBox())
         return;