Translate viewport related meta tags into @viewport descriptors as suggested by the CSS Device Adap…

Source/core/css/RuleSet.cpp

Index: Source/core/css/RuleSet.cpp
diff --git a/Source/core/css/RuleSet.cpp b/Source/core/css/RuleSet.cpp
index 85b4302136f2c93baa5da995b9784fa173cb33e4..012fc9a8babf9d1313038fb09ad6904071f4d717 100644
--- a/Source/core/css/RuleSet.cpp
+++ b/Source/core/css/RuleSet.cpp
@@ -391,8 +391,7 @@ void RuleSet::addChildRules(const Vector<RefPtr<StyleRuleBase> >& rules, const M
             resolver->setBuildScopedStyleTreeInDocumentOrder(false);
             resolver->ensureScopedStyleResolver(scope->shadowHost())->addHostRule(static_cast<StyleRuleHost*>(rule), hasDocumentSecurityOrigin, scope);
             resolver->setBuildScopedStyleTreeInDocumentOrder(enabled);
-        } else if (RuntimeEnabledFeatures::cssViewportEnabled() && rule->isViewportRule()) {
-            // @viewport should not be scoped.
+        } else if (rule->isViewportRule()) {
             if (!isDocumentScope(scope))
                 continue;
             addViewportRule(static_cast<StyleRuleViewport*>(rule));