Don't always have to relayout a child when fragmentainer height is unknown.

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 5aad7f755841285c46b4aeb9ace8980f0c7075c0..76ef83016c55f1928b4f1a5be12b937b5fef57ba 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -4742,7 +4742,9 @@ bool LayoutBox::childNeedsRelayoutForPagination(const LayoutBox& child) const {
       // have to. So we need to relayout.
       return true;
     }
-  } else {
+  } else if (child.offsetToNextPage()) {
+    // This child did previously break, but it won't anymore, because we no
+    // longer have a known fragmentainer height.
     return true;
   }