Add number() static methods to AtomicString class

Source/core/html/HTMLBodyElement.cpp

Index: Source/core/html/HTMLBodyElement.cpp
diff --git a/Source/core/html/HTMLBodyElement.cpp b/Source/core/html/HTMLBodyElement.cpp
index e31e3414741b93e407ecac5f5c16db1b6a58f842..44a1572fec5ff40e3e30c777fdd92ae2ba824d36 100644
--- a/Source/core/html/HTMLBodyElement.cpp
+++ b/Source/core/html/HTMLBodyElement.cpp
@@ -166,10 +166,10 @@ Node::InsertionNotificationRequest HTMLBodyElement::insertedInto(ContainerNode*
             HTMLFrameElementBase* ownerFrameElement = toHTMLFrameElementBase(ownerElement);
             int marginWidth = ownerFrameElement->marginWidth();
             if (marginWidth != -1)
-                setAttribute(marginwidthAttr, String::number(marginWidth));
+                setIntegralAttribute(marginwidthAttr, marginWidth);
             int marginHeight = ownerFrameElement->marginHeight();
             if (marginHeight != -1)
-                setAttribute(marginheightAttr, String::number(marginHeight));
+                setIntegralAttribute(marginheightAttr, marginHeight);
         }
     }
     return InsertionDone;