Clear box from percentage descendants when it is split off from the ancestor

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 a1e1e396a0a688ec1b942d21d6eff193c8a2119e..74ebd411405f714030916ce3fd7fe9eb62324e5e 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
@@ -654,6 +654,21 @@ void LayoutBlock::makeChildrenInlineIfPossible()
     setChildrenInline(true);
 }
 
+bool LayoutBlock::collapseLoneAnonymousBlock(LayoutBlock* child)
+{
+    if (!child->isAnonymousBlock())
+        return false;
+    if (child->beingDestroyed())

[mstensho (USE GERRIT), 2016/01/18 20:06:24]

Do you really need this? collapseAnonymousBlockChild() performs the same check
anyway. But you might end up returning true without the check, of course. Not
sure if that's a problem, though.

+        return false;
+    if (child->nextSibling() || child->continuation())

[mstensho (USE GERRIT), 2016/01/18 20:06:24]

Looks like we're missing a child->previousSibling() check. Not that it matters
with the current usage of this method, but this one's gonna sneak up on us from
behind at some point in the future when we least expect it. :)

+        return false;
+    LayoutBlock* parent = child->containingBlock();
+    if (parent->isRubyBase() || parent->isRubyRun())

[mstensho (USE GERRIT), 2016/01/18 20:06:24]

Ah... ruby, out of the blue. But I guess that's how it has to be. :( There's
canCollapseAnonymousBlockChild(), but no exception for ruby there...

+        return false;
+    collapseAnonymousBlockChild(parent, child);
+    return true;
+}
+
 void LayoutBlock::collapseAnonymousBlockChild(LayoutBlock* parent, LayoutBlock* child)
 {
     // It's possible that this block's destruction may have been triggered by the