Fieldset should allow whitespaces even though LayoutFlexibleBox doesn't.

third_party/WebKit/Source/core/dom/Text.cpp

Index: third_party/WebKit/Source/core/dom/Text.cpp
diff --git a/third_party/WebKit/Source/core/dom/Text.cpp b/third_party/WebKit/Source/core/dom/Text.cpp
index 89d8f9b7e117e18cf10bf07a05200ee52fc68cca..7d5e50c1beaf5f0c95d8c2b804966ca16e7f5fd3 100644
--- a/third_party/WebKit/Source/core/dom/Text.cpp
+++ b/third_party/WebKit/Source/core/dom/Text.cpp
@@ -243,8 +243,9 @@ Node* Text::cloneNode(bool /*deep*/)
 
 static inline bool canHaveWhitespaceChildren(const LayoutObject& parent)
 {
-    // <button> should allow whitespace even though LayoutFlexibleBox doesn't.
-    if (parent.isLayoutButton())
+    // <button> and <fieldset> should allow whitespace even though
+    // LayoutFlexibleBox doesn't.
+    if (parent.isLayoutButton() || parent.isFieldset())
         return true;
 
     if (parent.isTable() || parent.isTableRow() || parent.isTableSection()