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

Source/core/dom/StyleSheetCollection.cpp

Index: Source/core/dom/StyleSheetCollection.cpp
diff --git a/Source/core/dom/StyleSheetCollection.cpp b/Source/core/dom/StyleSheetCollection.cpp
index 5164c84de32fb73431c39cd79b5831e872330bca..9380b8af000ef4008e0b001776bf9cd949fe464e 100644
--- a/Source/core/dom/StyleSheetCollection.cpp
+++ b/Source/core/dom/StyleSheetCollection.cpp
@@ -40,6 +40,7 @@
 #include "core/dom/ProcessingInstruction.h"
 #include "core/html/HTMLIFrameElement.h"
 #include "core/html/HTMLLinkElement.h"
+#include "core/html/HTMLMetaElement.h"
 #include "core/html/HTMLStyleElement.h"
 #include "core/page/Page.h"
 #include "core/page/PageGroup.h"
@@ -104,7 +105,7 @@ void StyleSheetCollection::collectStyleSheets(DocumentStyleSheetCollection* coll
             sheet = pi->sheet();
             if (sheet && !sheet->disabled() && sheet->isCSSStyleSheet())
                 activeSheet = static_cast<CSSStyleSheet*>(sheet);
-        } else if ((n->isHTMLElement() && (n->hasTagName(linkTag) || n->hasTagName(styleTag))) || (n->isSVGElement() && n->hasTagName(SVGNames::styleTag))) {
+        } else if ((n->isHTMLElement() && (n->hasTagName(linkTag) || n->hasTagName(styleTag) || n->hasTagName(metaTag))) || (n->isSVGElement() && n->hasTagName(SVGNames::styleTag))) {
             Element* e = toElement(n);
             AtomicString title = e->getAttribute(titleAttr);
             bool enabledViaScript = false;
@@ -129,8 +130,10 @@ void StyleSheetCollection::collectStyleSheets(DocumentStyleSheetCollection* coll
                     title = nullAtom;
             } else if (n->isSVGElement() && n->hasTagName(SVGNames::styleTag)) {
                 sheet = static_cast<SVGStyleElement*>(n)->sheet();
-            } else {
+            } else if (n->hasTagName(styleTag)) {
                 sheet = static_cast<HTMLStyleElement*>(n)->sheet();
+            } else {
+                sheet = static_cast<HTMLMetaElement*>(n)->sheet();
             }
 
             if (sheet && !sheet->disabled() && sheet->isCSSStyleSheet())