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

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

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 92342e025981d09bbb700ce959d588a3b27c7fc8..c683aabf8caa3e0bcd247ee7dff783b73ed303be 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -4373,12 +4373,11 @@ static void markBoxForRelayoutAfterSplit(LayoutBox* box)
 
 LayoutObject* LayoutBox::splitAnonymousBoxesAroundChild(LayoutObject* beforeChild)
 {
-    bool didSplitParentAnonymousBoxes = false;
+    LayoutBox* boxAtTopOfNewBranch = nullptr;
 
     while (beforeChild->parent() != this) {
         LayoutBox* boxToSplit = toLayoutBox(beforeChild->parent());
         if (boxToSplit->slowFirstChild() != beforeChild && boxToSplit->isAnonymous()) {
-            didSplitParentAnonymousBoxes = true;
 
             // We have to split the parent box into two boxes and move children
             // from |beforeChild| to end into the new post box.
@@ -4394,6 +4393,7 @@ LayoutObject* LayoutBox::splitAnonymousBoxesAroundChild(LayoutObject* beforeChil
 
             markBoxForRelayoutAfterSplit(boxToSplit);
             markBoxForRelayoutAfterSplit(postBox);
+            boxAtTopOfNewBranch = postBox;
 
             beforeChild = postBox;
         } else {
@@ -4401,7 +4401,12 @@ LayoutObject* LayoutBox::splitAnonymousBoxesAroundChild(LayoutObject* beforeChil
         }
     }
 
-    if (didSplitParentAnonymousBoxes)
+    // Splitting the box means the left side of the container chain will lose any percent height descendants
+    // below |boxAtTopOfNewBranch| on the right hand side.
+    if (boxAtTopOfNewBranch && LayoutBlock::hasPercentHeightContainerMap())
+        LayoutBlock::clearPercentHeightDescendantsFrom(boxAtTopOfNewBranch);
+
+    if (boxAtTopOfNewBranch)

[mstensho (USE GERRIT), 2016/01/25 19:37:07]

We could if for |boxAtTopOfNewBranch| only once.

if (boxAtTopOfNewBranch) {
    // bla bla
    if (LayoutBlock::hasPercentHeightContainerMap())
        LayoutBlock::clearPercentHeightDescendantsFrom(boxAtTopOfNewBranch);

    markBoxForRelayoutAfterSplit(this);
}

         markBoxForRelayoutAfterSplit(this);
 
     ASSERT(beforeChild->parent() == this);