HTML Imports: Teach preloader about HTML Imports.

Source/core/html/parser/HTMLPreloadScanner.cpp

Index: Source/core/html/parser/HTMLPreloadScanner.cpp
diff --git a/Source/core/html/parser/HTMLPreloadScanner.cpp b/Source/core/html/parser/HTMLPreloadScanner.cpp
index 706fb0e51034b954e74e60534ba1610ac8e53691..4cf24d343d4710487a4e3823265229f09a760ee2 100644
--- a/Source/core/html/parser/HTMLPreloadScanner.cpp
+++ b/Source/core/html/parser/HTMLPreloadScanner.cpp
@@ -106,6 +106,7 @@ public:
     StartTagScanner(const StringImpl* tagImpl, PassRefPtr<MediaValues> mediaValues)
         : m_tagImpl(tagImpl)
         , m_linkIsStyleSheet(false)
+        , m_linkIsImport(false)
         , m_matchedMediaAttribute(true)
         , m_inputIsImage(false)
         , m_imgSourceSize(0)
@@ -193,14 +194,16 @@ private:
                 }
             }
         } else if (match(m_tagImpl, linkTag)) {
-            if (match(attributeName, hrefAttr))
+            if (match(attributeName, hrefAttr)) {
                 setUrlToLoad(attributeValue, DisallowURLReplacement);
-            else if (match(attributeName, relAttr))
+            } else if (match(attributeName, relAttr)) {
                 m_linkIsStyleSheet = relAttributeIsStyleSheet(attributeValue);
-            else if (match(attributeName, mediaAttr))
+                m_linkIsImport = RuntimeEnabledFeatures::htmlImportsEnabled() && relAttributeIsImport(attributeValue);
+            } else if (match(attributeName, mediaAttr)) {
                 m_matchedMediaAttribute = mediaAttributeMatches(*m_mediaValues, attributeValue);
-            else if (match(attributeName, crossoriginAttr))
+            } else if (match(attributeName, crossoriginAttr)) {
                 setCrossOriginAllowed(attributeValue);
+            }
         } else if (match(m_tagImpl, inputTag)) {
             if (match(attributeName, srcAttr))
                 setUrlToLoad(attributeValue, DisallowURLReplacement);
@@ -209,10 +212,21 @@ private:
         }
     }
 
+    static bool relAttributeWillBeImmediatelyUsed(const LinkRelAttribute& rel)
+    {
+        return !rel.isAlternate() && rel.iconType() == InvalidIcon && !rel.isDNSPrefetch();
+    }
+
     static bool relAttributeIsStyleSheet(const String& attributeValue)
     {
         LinkRelAttribute rel(attributeValue);
-        return rel.isStyleSheet() && !rel.isAlternate() && rel.iconType() == InvalidIcon && !rel.isDNSPrefetch();
+        return rel.isStyleSheet() && relAttributeWillBeImmediatelyUsed(rel);
+    }
+
+    static bool relAttributeIsImport(const String& attributeValue)
+    {
+        LinkRelAttribute rel(attributeValue);
+        return rel.isImport() && relAttributeWillBeImmediatelyUsed(rel);
     }
 
     void setUrlToLoad(const String& value, URLReplacement replacement)
@@ -243,6 +257,8 @@ private:
             return Resource::Image;
         if (match(m_tagImpl, linkTag) && m_linkIsStyleSheet)
             return Resource::CSSStyleSheet;
+        if (match(m_tagImpl, linkTag) && m_linkIsImport)
+            return Resource::ImportResource;
         ASSERT_NOT_REACHED();
         return Resource::Raw;
     }
@@ -251,7 +267,7 @@ private:
     {
         if (m_urlToLoad.isEmpty())
             return false;
-        if (match(m_tagImpl, linkTag) && !m_linkIsStyleSheet)
+        if (match(m_tagImpl, linkTag) && !m_linkIsStyleSheet && !m_linkIsImport)
             return false;
         if (match(m_tagImpl, inputTag) && !m_inputIsImage)
             return false;
@@ -282,6 +298,7 @@ private:
     ImageCandidate m_srcsetImageCandidate;
     String m_charset;
     bool m_linkIsStyleSheet;
+    bool m_linkIsImport;
     bool m_matchedMediaAttribute;
     bool m_inputIsImage;
     String m_imgSrcUrl;