Use css-device-adapt constraining for legacy viewport tags.

Source/core/css/CSSDefaultStyleSheets.h

Index: Source/core/css/CSSDefaultStyleSheets.h
diff --git a/Source/core/css/CSSDefaultStyleSheets.h b/Source/core/css/CSSDefaultStyleSheets.h
index e3469f39b76a0d31729e06eecb0644424c1faf02..827376780b111bd9b9daaf1759e614767ccd951e 100644
--- a/Source/core/css/CSSDefaultStyleSheets.h
+++ b/Source/core/css/CSSDefaultStyleSheets.h
@@ -35,6 +35,7 @@ public:
     static RuleSet* defaultQuirksStyle;
     static RuleSet* defaultPrintStyle;
     static RuleSet* defaultViewSourceStyle;
+    static RuleSet* defaultXHTMLMobileProfileStyle;
 
     static StyleSheetContents* simpleDefaultStyleSheet;
     static StyleSheetContents* defaultStyleSheet;
@@ -49,6 +50,7 @@ public:
     static void loadSimpleDefaultStyle();
     static void initDefaultStyle(Element*);
     static RuleSet* viewSourceStyle();
+    static RuleSet* xhtmlMobileProfileStyle();
 };
 
 } // namespace WebCore