Implement all shorthand property.

Source/core/css/StylePropertySerializer.cpp

Index: Source/core/css/StylePropertySerializer.cpp
diff --git a/Source/core/css/StylePropertySerializer.cpp b/Source/core/css/StylePropertySerializer.cpp
index 489527ff68ed9749d3c74d15df57866d0680d099..161d2554dcea7d384c6354564c2fd7e607da1961 100644
--- a/Source/core/css/StylePropertySerializer.cpp
+++ b/Source/core/css/StylePropertySerializer.cpp
@@ -67,6 +67,15 @@ String StylePropertySerializer::asText() const
     BitArray<numCSSProperties> shorthandPropertyAppeared;
 
     unsigned size = m_propertySet.propertyCount();
+
+    // FIXME: need to support "unset".
+    // 'all' property: http://dev.w3.org/csswg/css-cascade/#all-shorthand
+    // 'unset" value: http://dev.w3.org/csswg/css-cascade/#unset
+    if (size == allShorthand().length() && shorthandHasOnlyInitialOrInheritedValue(allShorthand())) {
+        StylePropertySet::PropertyReference property = m_propertySet.propertyAt(0);
+        return getPropertyText(CSSPropertyAll, getCommonValue(allShorthand()), property.isImportant(), false);
+    }
+
     unsigned numDecls = 0;
     for (unsigned n = 0; n < size; ++n) {
         StylePropertySet::PropertyReference property = m_propertySet.propertyAt(n);