Add grid/flex layout support for <fieldset>

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

Index: third_party/WebKit/Source/core/layout/LayoutBlock.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
index 754ba3498df89678cbba151237cb7186ba27e57c..aa168c705caae130069e675a83d768a01a5bb248 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
@@ -332,6 +332,9 @@ void LayoutBlock::removeLeftoverAnonymousBlock(LayoutBlock* child)
     if (child->continuation())
         return;
 
+    if (isFieldset())
+        return;
+
     // Promote all the leftover anonymous block's children (to become children of this block
     // instead). We still want to keep the leftover block in the tree for a moment, for notification
     // purposes done further below (flow threads and grids).
@@ -1740,6 +1743,9 @@ LayoutBlock* LayoutBlock::createAnonymousWithParentAndDisplay(const LayoutObject
     if (display == FLEX || display == INLINE_FLEX) {
         newBox = LayoutFlexibleBox::createAnonymous(&parent->document());
         newDisplay = FLEX;
+    } else if (display == GRID || display == INLINE_GRID) {
+        newBox = LayoutGrid::createAnonymous(&parent->document());
+        newDisplay = GRID;
     } else {
         newBox = LayoutBlockFlow::createAnonymous(&parent->document());
         newDisplay = BLOCK;