Empty @viewport should not override legacy viewport.

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 1046 matching lines @@
     m_styleResourceLoader.loadPendingResources(state.style(), state.elementStyleResources());
 
     document().didAccessStyleResolver();
 
     // Now return the style.
     return state.takeStyle();
 }
 
 void StyleResolver::collectViewportRules()
 {
-    collectViewportRules(CSSDefaultStyleSheets::defaultStyle, UserAgentOrigin);
+    viewportStyleResolver()->collectViewportRules(CSSDefaultStyleSheets::defaultStyle, ViewportStyleResolver::UserAgentOrigin);
 
     if (document().isMobileDocument())
-        collectViewportRules(CSSDefaultStyleSheets::xhtmlMobileProfileStyle(), UserAgentOrigin);
+        viewportStyleResolver()->collectViewportRules(CSSDefaultStyleSheets::xhtmlMobileProfileStyle(), ViewportStyleResolver::UserAgentOrigin);
 
     if (m_ruleSets.userStyle())
-        collectViewportRules(m_ruleSets.userStyle(), UserAgentOrigin);
+        viewportStyleResolver()->collectViewportRules(m_ruleSets.userStyle(), ViewportStyleResolver::UserAgentOrigin);
 
     if (ScopedStyleResolver* scopedResolver = m_styleTree.scopedStyleResolverForDocument())
         scopedResolver->collectViewportRulesTo(this);
 
     viewportStyleResolver()->resolve();
 }
 
-void StyleResolver::collectViewportRules(RuleSet* rules, ViewportOrigin origin)
-{
-    rules->compactRulesIfNeeded();
-
-    const Vector<StyleRuleViewport*>& viewportRules = rules->viewportRules();
-    if (origin == AuthorOrigin && viewportRules.size())
-        viewportStyleResolver()->setHasAuthorStyle();
-    for (size_t i = 0; i < viewportRules.size(); ++i)
-        viewportStyleResolver()->addViewportRule(viewportRules[i]);
-}
-
 PassRefPtr<RenderStyle> StyleResolver::defaultStyleForElement()
 {
     StyleResolverState state(document(), 0);
     state.setStyle(RenderStyle::create());
     state.fontBuilder().initForStyleResolve(document(), state.style(), state.useSVGZoomRules());
     state.style()->setLineHeight(RenderStyle::initialLineHeight());
     state.setLineHeightValue(0);
     state.fontBuilder().setInitial(state.style()->effectiveZoom());
     state.style()->font().update(fontSelector());
     return state.takeStyle();
@@ skipping 503 matching lines @@
         m_matchedPropertiesSearches, m_matchedPropertiesHit, m_matchedPropertiesSharedInheritedHit, m_matchedPropertiesToCache, m_matchedPropertiesEnteredIntoCache);
 
     fprintf(stderr, "Total:\n");
     printStyleStats(m_totalSearches, m_totalElementsEligibleForSharing, m_totalStylesShared, m_totalSearchFoundSiblingForSharing, m_totalSearchesMissedSharing,
         m_totalMatchedPropertiesSearches, m_totalMatchedPropertiesHit, m_totalMatchedPropertiesSharedInheritedHit, m_totalMatchedPropertiesToCache, m_totalMatchedPropertiesEnteredIntoCache);
     fprintf(stderr, "--------------------------------------------------------------------------------\n");
 }
 #endif
 
 } // namespace WebCore