Collect @viewport before constructing RuleSets.

third_party/WebKit/Source/core/dom/StyleEngine.h

Index: third_party/WebKit/Source/core/dom/StyleEngine.h
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.h b/third_party/WebKit/Source/core/dom/StyleEngine.h
index 7529ec1ec0dcbcab4038b163885a160aed1c80cb..fdd320beddde2b5525df8a7fb4fbbefea2316f28 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.h
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.h
@@ -58,6 +58,7 @@ class ShadowTreeStyleSheetCollection;
 class StyleRuleFontFace;
 class StyleSheet;
 class StyleSheetContents;
+class ViewportStyleResolver;
 
 class CORE_EXPORT StyleEngine final
     : public GarbageCollectedFinalized<StyleEngine>,
@@ -100,6 +101,8 @@ class CORE_EXPORT StyleEngine final
   void removeStyleSheetCandidateNode(Node&, TreeScope&);
   void modifiedStyleSheetCandidateNode(Node&);
   void watchedSelectorsChanged();
+  void initialViewportChanged();
+  void viewportRulesChanged();
 
   void injectAuthorSheet(StyleSheetContents* authorSheet);
   CSSStyleSheet& ensureInspectorStyleSheet();
@@ -161,6 +164,7 @@ class CORE_EXPORT StyleEngine final
     if (!m_resolver) {
       createResolver();
     } else if (m_resolver->hasPendingAuthorStyleSheets()) {
+      viewportRulesChanged();
       m_resolver->appendPendingAuthorStyleSheets();
     }
     return *m_resolver.get();
@@ -313,6 +317,7 @@ class CORE_EXPORT StyleEngine final
   bool m_didCalculateResolver = false;
 
   Member<StyleResolver> m_resolver;
+  Member<ViewportStyleResolver> m_viewportResolver;
   StyleInvalidator m_styleInvalidator;
 
   Member<CSSFontSelector> m_fontSelector;