New parser mode for CSSOM @viewport descriptors.

Source/core/css/StylePropertySet.cpp

Index: Source/core/css/StylePropertySet.cpp
diff --git a/Source/core/css/StylePropertySet.cpp b/Source/core/css/StylePropertySet.cpp
index 7f906ea77f85182dee7ba68b808a1259be93c1b6..8df65b850b2c61cd7b3fc2056dc228650bf3e486 100644
--- a/Source/core/css/StylePropertySet.cpp
+++ b/Source/core/css/StylePropertySet.cpp
@@ -80,7 +80,7 @@ ImmutableStylePropertySet::ImmutableStylePropertySet(const CSSProperty* properti
 {
     StylePropertyMetadata* metadataArray = const_cast<StylePropertyMetadata*>(this->metadataArray());
     CSSValue** valueArray = const_cast<CSSValue**>(this->valueArray());
-    for (unsigned i = 0; i < length; ++i) {
+    for (unsigned i = 0; i < m_arraySize; ++i) {
         metadataArray[i] = properties[i].metadata();
         valueArray[i] = properties[i].value();
         valueArray[i]->ref();