Recalc styles on resize if we have viewport units.

Source/WebCore/dom/DocumentStyleSheetCollection.cpp

Index: Source/WebCore/dom/DocumentStyleSheetCollection.cpp
diff --git a/Source/WebCore/dom/DocumentStyleSheetCollection.cpp b/Source/WebCore/dom/DocumentStyleSheetCollection.cpp
index 232b5e2d634c2d794610a658ccf5ffd84cfaf741..31458f8982cd489f45d52d10ec9b90bfc4e3726c 100644
--- a/Source/WebCore/dom/DocumentStyleSheetCollection.cpp
+++ b/Source/WebCore/dom/DocumentStyleSheetCollection.cpp
@@ -68,6 +68,7 @@ DocumentStyleSheetCollection::DocumentStyleSheetCollection(Document* document)
     , m_usesBeforeAfterRules(false)
     , m_usesBeforeAfterRulesOverride(false)
     , m_usesRemUnits(false)
+    , m_usesViewportUnits(false)
 {
 }
 
@@ -427,6 +428,15 @@ static bool styleSheetsUseRemUnits(const Vector<RefPtr<CSSStyleSheet> >& sheets)
     return false;
 }
 
+static bool styleSheetsUseViewportUnits(const Vector<RefPtr<CSSStyleSheet> >& sheets)
+{
+    for (unsigned i = 0; i < sheets.size(); ++i) {
+        if (sheets[i]->contents()->usesViewportUnits())
+            return true;
+    }
+    return false;
+}
+
 static void filterEnabledCSSStyleSheets(Vector<RefPtr<CSSStyleSheet> >& result, const Vector<RefPtr<StyleSheet> >& sheets)
 {
     for (unsigned i = 0; i < sheets.size(); ++i) {
@@ -490,6 +500,7 @@ bool DocumentStyleSheetCollection::updateActiveStyleSheets(UpdateFlag updateFlag
     m_styleSheetsForStyleSheetList.swap(activeStyleSheets);
 
     m_usesRemUnits = styleSheetsUseRemUnits(m_activeAuthorStyleSheets);
+    m_usesViewportUnits = styleSheetsUseViewportUnits(m_activeAuthorStyleSheets);
     m_needsUpdateActiveStylesheetsOnStyleRecalc = false;
 
     m_document->notifySeamlessChildDocumentsOfStylesheetUpdate();