Implement collection of @viewport rules from DocumentStyleCollection.

third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp

Index: third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp
diff --git a/third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp b/third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp
index 8ab9f07dee602a2292951304a3cb6f7126be80ff..1a8d918e5ebdfe41a5d9fe729260ee80f7e3b7d0 100644
--- a/third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp
+++ b/third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.cpp
@@ -29,6 +29,7 @@
 #include "core/dom/DocumentStyleSheetCollection.h"
 
 #include "core/css/resolver/StyleResolver.h"
+#include "core/css/resolver/ViewportStyleResolver.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentStyleSheetCollector.h"
 #include "core/dom/ProcessingInstruction.h"
@@ -130,4 +131,22 @@ void DocumentStyleSheetCollection::updateActiveStyleSheets(
   collection->dispose();
 }
 
+void DocumentStyleSheetCollection::collectViewportRules(
+    ViewportStyleResolver& viewportResolver) {
+  for (Node* node : m_styleSheetCandidateNodes) {
+    StyleSheetCandidate candidate(*node);
+
+    if (candidate.isImport())
+      continue;
+    StyleSheet* sheet = candidate.sheet();
+    if (!sheet)
+      continue;
+    if (!candidate.canBeActivated(
+            document().styleEngine().preferredStylesheetSetName()))
+      continue;
+    viewportResolver.collectViewportRulesFromAuthorSheet(
+        *toCSSStyleSheet(sheet));
+  }
+}
+
 }  // namespace blink