Empty @viewport should not override legacy viewport.

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 7d34c1c50d779b90588ebb348dc5f746f498d382..924b2c1f104e5f49514cc695e5f5512661c0d2a6 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -1064,13 +1064,13 @@ PassRefPtr<RenderStyle> StyleResolver::styleForPage(int pageIndex)
 
 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);
@@ -1078,17 +1078,6 @@ void StyleResolver::collectViewportRules()
     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);