Move viewport unit resolution to style recalc time

Source/core/dom/TreeScope.cpp

Index: Source/core/dom/TreeScope.cpp
diff --git a/Source/core/dom/TreeScope.cpp b/Source/core/dom/TreeScope.cpp
index a54da2e6e3f33204f3cecd35781fb7aff03572d3..d7ad63c60921bc35376d07407a110f06aa24d925 100644
--- a/Source/core/dom/TreeScope.cpp
+++ b/Source/core/dom/TreeScope.cpp
@@ -33,6 +33,7 @@
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/IdTargetObserverRegistry.h"
+#include "core/dom/NodeRenderStyle.h"
 #include "core/dom/TreeScopeAdopter.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
@@ -507,4 +508,15 @@ Element* TreeScope::getElementByAccessKey(const String& key) const
     return result;
 }
 
+void TreeScope::setNeedsStyleRecalcForViewportUnits()
+{
+    for (Element* element = ElementTraversal::firstWithin(*rootNode()); element; element = ElementTraversal::nextIncludingPseudo(*element)) {
+        for (ShadowRoot* root = element->youngestShadowRoot(); root; root = root->olderShadowRoot())
+            root->setNeedsStyleRecalcForViewportUnits();
+        RenderStyle* style = element->renderStyle();
+        if (style && style->hasViewportUnits())
+            element->setNeedsStyleRecalc(LocalStyleChange);
+    }
+}
+
 } // namespace WebCore