Add link preload as=document support

third_party/WebKit/Source/core/loader/LinkLoader.cpp

Index: third_party/WebKit/Source/core/loader/LinkLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/LinkLoader.cpp b/third_party/WebKit/Source/core/loader/LinkLoader.cpp
index 208b30de570ab9194c954f28b6ee10ccecb8cf34..a4e9894daef421bf9c6d189e7f7b588501689831 100644
--- a/third_party/WebKit/Source/core/loader/LinkLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/LinkLoader.cpp
@@ -186,6 +186,8 @@ bool LinkLoader::getResourceTypeFromAsAttribute(const String& as, Resource::Type
         type = Resource::Font;
     } else if (as == "track") {
         type = Resource::TextTrack;
+    } else if (as == "document") {
+        type = Resource::MainResource;
     } else {
         type = Resource::Raw;
         if (!as.isEmpty())
@@ -211,6 +213,9 @@ void LinkLoader::createLinkPreloadResourceClient(Resource* resource)
     case Resource::Font:
         m_linkPreloadResourceClient = LinkPreloadFontResourceClient::create(this, toFontResource(resource));
         break;
+    case Resource::MainResource:
+        m_linkPreloadResourceClient = LinkPreloadRawResourceClient::create(this, toRawResource(resource));
+        break;
     case Resource::Media:
     case Resource::TextTrack:
     case Resource::Raw:
@@ -239,6 +244,7 @@ static bool isSupportedType(Resource::Type resourceType, const String& mimeType)
     case Resource::TextTrack:
         return MIMETypeRegistry::isSupportedTextTrackMIMEType(mimeType);
     case Resource::Raw:
+    case Resource::MainResource:
         return true;
     default:
         ASSERT_NOT_REACHED();
@@ -283,6 +289,8 @@ static Resource* preloadIfNeeded(const LinkRelAttribute& relAttribute, const KUR
         return nullptr;
     }
     ResourceRequest resourceRequest(document.completeURL(href));
+    if (resourceType == Resource::MainResource)
+        resourceRequest.setFrameType(WebURLRequest::FrameTypePreload);
     ResourceFetcher::determineRequestContext(resourceRequest, resourceType, false);
     FetchRequest linkRequest(resourceRequest, FetchInitiatorTypeNames::link, document.encodingName());