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

Source/core/css/CSSParser-in.cpp

Index: Source/core/css/CSSParser-in.cpp
diff --git a/Source/core/css/CSSParser-in.cpp b/Source/core/css/CSSParser-in.cpp
index edbc75075ee64421e897194648fb9f368b0c3791..6dea4f999953ee28d7280f3cd4557a52640168df 100644
--- a/Source/core/css/CSSParser-in.cpp
+++ b/Source/core/css/CSSParser-in.cpp
@@ -2847,13 +2847,14 @@ bool CSSParser::parseValue(CSSPropertyID propId, bool important)
         // These properties should be handled before in isValidKeywordPropertyAndValue().
         ASSERT_NOT_REACHED();
         return false;
-    // Properties bellow are validated inside parseViewportProperty, because we
+    // Properties below are validated inside parseViewportProperty, because we
     // check for parser state inViewportScope. We need to invalidate if someone
     // adds them outside a @viewport rule.
     case CSSPropertyMaxZoom:
     case CSSPropertyMinZoom:
     case CSSPropertyOrientation:
     case CSSPropertyUserZoom:
+    case CSSPropertyInternalPriority:
         validPrimitive = false;
         break;
     default:
@@ -11610,9 +11611,6 @@ unsigned CSSParser::safeUserStringTokenOffset()
 
 StyleRuleBase* CSSParser::createViewportRule()
 {
-    if (!RuntimeEnabledFeatures::cssViewportEnabled())
-        return 0;
-
     m_allowImportRules = m_allowNamespaceDeclarations = false;
 
     RefPtr<StyleRuleViewport> rule = StyleRuleViewport::create();
@@ -11629,8 +11627,6 @@ StyleRuleBase* CSSParser::createViewportRule()
 
 bool CSSParser::parseViewportProperty(CSSPropertyID propId, bool important)
 {
-    ASSERT(RuntimeEnabledFeatures::cssViewportEnabled());
-
     CSSParserValue* value = m_valueList->current();
     if (!value)
         return false;
@@ -11639,6 +11635,12 @@ bool CSSParser::parseViewportProperty(CSSPropertyID propId, bool important)
     bool validPrimitive = false;
 
     switch (propId) {
+    case CSSPropertyInternalPriority:
+        if (id == CSSValueAuto)
+            validPrimitive = true;
+        else
+            validPrimitive = (!id && validUnit(value, FNumber | FNonNeg));
+        break;
     case CSSPropertyMinWidth: // auto | extend-to-zoom | <length> | <percentage>
     case CSSPropertyMaxWidth:
     case CSSPropertyMinHeight:
@@ -11689,7 +11691,6 @@ bool CSSParser::parseViewportProperty(CSSPropertyID propId, bool important)
 
 bool CSSParser::parseViewportShorthand(CSSPropertyID propId, CSSPropertyID first, CSSPropertyID second, bool important)
 {
-    ASSERT(RuntimeEnabledFeatures::cssViewportEnabled());
     unsigned numValues = m_valueList->size();
 
     if (numValues > 2)