NetworkProcess: DNS prefetch happens in the Web Process
authorcarlosgc@webkit.org <carlosgc@webkit.org@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Wed, 21 Oct 2015 08:08:48 +0000 (08:08 +0000)
committercarlosgc@webkit.org <carlosgc@webkit.org@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Wed, 21 Oct 2015 08:08:48 +0000 (08:08 +0000)
https://bugs.webkit.org/show_bug.cgi?id=147824

Reviewed by Chris Dumez.

Source/WebCore:

Use FrameLoaderClient to do the DNS prefetch.

* html/HTMLAnchorElement.cpp:
(WebCore::HTMLAnchorElement::parseAttribute):
* loader/EmptyClients.h:
* loader/FrameLoaderClient.h:
* loader/LinkLoader.cpp:
(WebCore::LinkLoader::loadLink):
* page/Chrome.cpp:
(WebCore::Chrome::mouseDidMoveOverElement):

Source/WebKit/mac:

Implement FrameLoaderClient::prefetchDNS().

* WebCoreSupport/WebFrameLoaderClient.h:
* WebCoreSupport/WebFrameLoaderClient.mm:

Source/WebKit/win:

Implement FrameLoaderClient::prefetchDNS().

* WebCoreSupport/WebFrameLoaderClient.cpp:
(WebFrameLoaderClient::prefetchDNS):
* WebCoreSupport/WebFrameLoaderClient.h:

Source/WebKit2:

DNS prefetch requests started in the WebProcess should be sent to
the network process when it's enabled.

* NetworkProcess/NetworkConnectionToWebProcess.cpp:
(WebKit::NetworkConnectionToWebProcess::prefetchDNS): Use NetworkProcess::prefetchDNS().
* NetworkProcess/NetworkConnectionToWebProcess.h:
* NetworkProcess/NetworkConnectionToWebProcess.messages.in: Add
PrefetchDNS message.
* NetworkProcess/NetworkProcess.cpp:
(WebKit::NetworkProcess::prefetchDNS): Do the actual DNS prefetch.
* NetworkProcess/NetworkProcess.h:
* WebProcess/InjectedBundle/API/gtk/WebKitWebExtension.cpp:
(webkitWebExtensionDidReceiveMessage): Use WebProcess::prefetchDNS().
* WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
(WebKit::WebFrameLoaderClient::prefetchDNS): Use WebProcess::prefetchDNS().
* WebProcess/WebCoreSupport/WebFrameLoaderClient.h:
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::sendTapHighlightForNodeIfNecessary): Use
FrameLoaderClient to do the DNS prefetch.
* WebProcess/WebProcess.cpp:
(WebKit::WebProcess::WebProcess): Initialize the DNS prefetched
hosts cleanup hysteresis activity. Clear the cache of DNS
prefetched when hysteresis activity stopped.
(WebKit::WebProcess::prefetchDNS): Send the request to the network
process if it's enabled, otherwise do the actual DNS prefetch.
* WebProcess/WebProcess.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@191381 268f45cc-cd09-0410-ab3c-d52691b4dbfc

24 files changed:
Source/WebCore/ChangeLog
Source/WebCore/html/HTMLAnchorElement.cpp
Source/WebCore/loader/EmptyClients.h
Source/WebCore/loader/FrameLoaderClient.h
Source/WebCore/loader/LinkLoader.cpp
Source/WebCore/page/Chrome.cpp
Source/WebKit/mac/ChangeLog
Source/WebKit/mac/WebCoreSupport/WebFrameLoaderClient.h
Source/WebKit/mac/WebCoreSupport/WebFrameLoaderClient.mm
Source/WebKit/win/ChangeLog
Source/WebKit/win/WebCoreSupport/WebFrameLoaderClient.cpp
Source/WebKit/win/WebCoreSupport/WebFrameLoaderClient.h
Source/WebKit2/ChangeLog
Source/WebKit2/NetworkProcess/NetworkConnectionToWebProcess.cpp
Source/WebKit2/NetworkProcess/NetworkConnectionToWebProcess.h
Source/WebKit2/NetworkProcess/NetworkConnectionToWebProcess.messages.in
Source/WebKit2/NetworkProcess/NetworkProcess.cpp
Source/WebKit2/NetworkProcess/NetworkProcess.h
Source/WebKit2/WebProcess/InjectedBundle/API/gtk/WebKitWebExtension.cpp
Source/WebKit2/WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp
Source/WebKit2/WebProcess/WebCoreSupport/WebFrameLoaderClient.h
Source/WebKit2/WebProcess/WebPage/ios/WebPageIOS.mm
Source/WebKit2/WebProcess/WebProcess.cpp
Source/WebKit2/WebProcess/WebProcess.h

index 9543e1e..26fc4b6 100644 (file)
@@ -1,3 +1,21 @@
+2015-10-21  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        NetworkProcess: DNS prefetch happens in the Web Process
+        https://bugs.webkit.org/show_bug.cgi?id=147824
+
+        Reviewed by Chris Dumez.
+
+        Use FrameLoaderClient to do the DNS prefetch.
+
+        * html/HTMLAnchorElement.cpp:
+        (WebCore::HTMLAnchorElement::parseAttribute):
+        * loader/EmptyClients.h:
+        * loader/FrameLoaderClient.h:
+        * loader/LinkLoader.cpp:
+        (WebCore::LinkLoader::loadLink):
+        * page/Chrome.cpp:
+        (WebCore::Chrome::mouseDidMoveOverElement):
+
 2015-10-21  Frederic Wang  <fred.wang@free.fr>
 
         [FreeType] Add support for the USE_TYPO_METRICS flag
index 2770250..9eaecfd 100644 (file)
@@ -25,7 +25,6 @@
 #include "HTMLAnchorElement.h"
 
 #include "AttributeDOMTokenList.h"
-#include "DNS.h"
 #include "ElementIterator.h"
 #include "EventHandler.h"
 #include "EventNames.h"
@@ -252,9 +251,9 @@ void HTMLAnchorElement::parseAttribute(const QualifiedName& name, const AtomicSt
             setNeedsStyleRecalc();
         if (isLink()) {
             String parsedURL = stripLeadingAndTrailingHTMLSpaces(value);
-            if (document().isDNSPrefetchEnabled()) {
+            if (document().isDNSPrefetchEnabled() && document().frame()) {
                 if (protocolIsInHTTPFamily(parsedURL) || parsedURL.startsWith("//"))
-                    prefetchDNS(document().completeURL(parsedURL).host());
+                    document().frame()->loader().client().prefetchDNS(document().completeURL(parsedURL).host());
             }
         }
         invalidateCachedVisitedLinkHash();
index dc115f4..b00124a 100644 (file)
@@ -400,6 +400,8 @@ public:
 #endif
 
     virtual bool isEmptyFrameLoaderClient() override { return true; }
+
+    virtual void prefetchDNS(const String&) override { }
 };
 
 class EmptyTextCheckerClient : public TextCheckerClient {
index a004a4d..2821cbb 100644 (file)
@@ -346,6 +346,8 @@ namespace WebCore {
 #if ENABLE(CONTENT_FILTERING)
         virtual void contentFilterDidBlockLoad(ContentFilterUnblockHandler) { }
 #endif
+
+        virtual void prefetchDNS(const String&) = 0;
     };
 
 } // namespace WebCore
index abbc00d..f69e26e 100644 (file)
@@ -37,7 +37,6 @@
 #include "CachedResourceLoader.h"
 #include "CachedResourceRequest.h"
 #include "ContainerNode.h"
-#include "DNS.h"
 #include "Document.h"
 #include "Frame.h"
 #include "FrameLoaderClient.h"
@@ -98,8 +97,8 @@ bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const URL& href,
         Settings* settings = document.settings();
         // FIXME: The href attribute of the link element can be in "//hostname" form, and we shouldn't attempt
         // to complete that as URL <https://bugs.webkit.org/show_bug.cgi?id=48857>.
-        if (settings && settings->dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty())
-            prefetchDNS(href.host());
+        if (settings && settings->dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty() && document.frame())
+            document.frame()->loader().client().prefetchDNS(href.host());
     }
 
 #if ENABLE(LINK_PREFETCH)
index 8013bea..8182b91 100644 (file)
 #include "Chrome.h"
 
 #include "ChromeClient.h"
-#include "DNS.h"
 #include "Document.h"
 #include "DocumentType.h"
 #include "FileIconLoader.h"
 #include "FileChooser.h"
 #include "FileList.h"
 #include "FloatRect.h"
+#include "FrameLoaderClient.h"
 #include "FrameTree.h"
 #include "Geolocation.h"
 #include "HTMLFormElement.h"
@@ -350,7 +350,7 @@ void Chrome::setStatusbarText(Frame* frame, const String& status)
 void Chrome::mouseDidMoveOverElement(const HitTestResult& result, unsigned modifierFlags)
 {
     if (result.innerNode() && result.innerNode()->document().isDNSPrefetchEnabled())
-        prefetchDNS(result.absoluteLinkURL().host());
+        m_page.mainFrame().loader().client().prefetchDNS(result.absoluteLinkURL().host());
     m_client.mouseDidMoveOverElement(result, modifierFlags);
 
     InspectorInstrumentation::mouseDidMoveOverElement(m_page, result, modifierFlags);
index 4d3b5a5..29f1511 100644 (file)
@@ -1,3 +1,15 @@
+2015-10-21  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        NetworkProcess: DNS prefetch happens in the Web Process
+        https://bugs.webkit.org/show_bug.cgi?id=147824
+
+        Reviewed by Chris Dumez.
+
+        Implement FrameLoaderClient::prefetchDNS().
+
+        * WebCoreSupport/WebFrameLoaderClient.h:
+        * WebCoreSupport/WebFrameLoaderClient.mm:
+
 2015-10-20  Commit Queue  <commit-queue@webkit.org>
 
         Unreviewed, rolling out r191370.
index 84e5456..b152ccf 100644 (file)
@@ -248,6 +248,8 @@ private:
     void contentFilterDidBlockLoad(WebCore::ContentFilterUnblockHandler) override;
 #endif
 
+    void prefetchDNS(const String&) override;
+
     RetainPtr<WebFrame> m_webFrame;
 
     RetainPtr<WebFramePolicyListener> m_policyListener;
index a4baa4a..c6ba23d 100644 (file)
@@ -79,6 +79,7 @@
 #import <WebCore/BlockExceptions.h>
 #import <WebCore/CachedFrame.h>
 #import <WebCore/Chrome.h>
+#import <WebCore/DNS.h>
 #import <WebCore/Document.h>
 #import <WebCore/DocumentLoader.h>
 #import <WebCore/EventHandler.h>
@@ -2288,6 +2289,11 @@ void WebFrameLoaderClient::contentFilterDidBlockLoad(WebCore::ContentFilterUnblo
 }
 #endif
 
+void WebFrameLoaderClient::prefetchDNS(const String& hostname)
+{
+    WebCore::prefetchDNS(hostname);
+}
+
 @implementation WebFramePolicyListener
 
 + (void)initialize
index 707c1bd..ba6b369 100644 (file)
@@ -1,3 +1,16 @@
+2015-10-21  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        NetworkProcess: DNS prefetch happens in the Web Process
+        https://bugs.webkit.org/show_bug.cgi?id=147824
+
+        Reviewed by Chris Dumez.
+
+        Implement FrameLoaderClient::prefetchDNS().
+
+        * WebCoreSupport/WebFrameLoaderClient.cpp:
+        (WebFrameLoaderClient::prefetchDNS):
+        * WebCoreSupport/WebFrameLoaderClient.h:
+
 2015-10-14  Simon Fraser  <simon.fraser@apple.com>
 
         Change GraphicsContext image-drawing functions to take references
index b90f896..72228c1 100644 (file)
@@ -60,6 +60,7 @@
 #include <JavaScriptCore/APICast.h>
 #include <WebCore/BackForwardController.h>
 #include <WebCore/CachedFrame.h>
+#include <WebCore/DNS.h>
 #include <WebCore/DocumentLoader.h>
 #include <WebCore/FormState.h>
 #include <WebCore/Frame.h>
@@ -1366,3 +1367,8 @@ void WebFrameLoaderClient::receivedPolicyDecision(PolicyAction action)
 
     function(action);
 }
+
+void WebFrameLoaderClient::prefetchDNS(const String& hostname)
+{
+    WebCore::prefetchDNS(hostname);
+}
index c184678..b1ff227 100644 (file)
@@ -203,6 +203,8 @@ public:
 
     virtual void dispatchDidFailToStartPlugin(const WebCore::PluginView*) const;
 
+    void prefetchDNS(const String&) override;
+
 protected:
     class WebFramePolicyListenerPrivate;
     std::unique_ptr<WebFramePolicyListenerPrivate> m_policyListenerPrivate;
index a5b9c4a..7a6eb06 100644 (file)
@@ -1,3 +1,37 @@
+2015-10-21  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        NetworkProcess: DNS prefetch happens in the Web Process
+        https://bugs.webkit.org/show_bug.cgi?id=147824
+
+        Reviewed by Chris Dumez.
+
+        DNS prefetch requests started in the WebProcess should be sent to
+        the network process when it's enabled.
+
+        * NetworkProcess/NetworkConnectionToWebProcess.cpp:
+        (WebKit::NetworkConnectionToWebProcess::prefetchDNS): Use NetworkProcess::prefetchDNS().
+        * NetworkProcess/NetworkConnectionToWebProcess.h:
+        * NetworkProcess/NetworkConnectionToWebProcess.messages.in: Add
+        PrefetchDNS message.
+        * NetworkProcess/NetworkProcess.cpp:
+        (WebKit::NetworkProcess::prefetchDNS): Do the actual DNS prefetch.
+        * NetworkProcess/NetworkProcess.h:
+        * WebProcess/InjectedBundle/API/gtk/WebKitWebExtension.cpp:
+        (webkitWebExtensionDidReceiveMessage): Use WebProcess::prefetchDNS().
+        * WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
+        (WebKit::WebFrameLoaderClient::prefetchDNS): Use WebProcess::prefetchDNS().
+        * WebProcess/WebCoreSupport/WebFrameLoaderClient.h:
+        * WebProcess/WebPage/ios/WebPageIOS.mm:
+        (WebKit::WebPage::sendTapHighlightForNodeIfNecessary): Use
+        FrameLoaderClient to do the DNS prefetch.
+        * WebProcess/WebProcess.cpp:
+        (WebKit::WebProcess::WebProcess): Initialize the DNS prefetched
+        hosts cleanup hysteresis activity. Clear the cache of DNS
+        prefetched when hysteresis activity stopped.
+        (WebKit::WebProcess::prefetchDNS): Send the request to the network
+        process if it's enabled, otherwise do the actual DNS prefetch.
+        * WebProcess/WebProcess.h:
+
 2015-10-20  Chris Dumez  <cdumez@apple.com>
 
         [WK2] Generalize NetworkCacheStorage API so it can store different types of metadata
index 82a20d5..968a341 100644 (file)
@@ -159,6 +159,11 @@ void NetworkConnectionToWebProcess::setDefersLoading(ResourceLoadIdentifier iden
     loader->setDefersLoading(defers);
 }
 
+void NetworkConnectionToWebProcess::prefetchDNS(const String& hostname)
+{
+    NetworkProcess::singleton().prefetchDNS(hostname);
+}
+
 static NetworkStorageSession& storageSession(SessionID sessionID)
 {
     if (sessionID.isEphemeral()) {
index 822de58..1c03e95 100644 (file)
@@ -73,6 +73,7 @@ private:
     void scheduleResourceLoad(const NetworkResourceLoadParameters&);
     void performSynchronousLoad(const NetworkResourceLoadParameters&, PassRefPtr<Messages::NetworkConnectionToWebProcess::PerformSynchronousLoad::DelayedReply>);
     void loadPing(const NetworkResourceLoadParameters&);
+    void prefetchDNS(const String&);
 
     void removeLoadIdentifier(ResourceLoadIdentifier);
     void setDefersLoading(ResourceLoadIdentifier, bool);
index 4c0a7ad..39aeffd 100644 (file)
@@ -29,6 +29,7 @@ messages -> NetworkConnectionToWebProcess LegacyReceiver {
     LoadPing(WebKit::NetworkResourceLoadParameters resourceLoadParameters)
     RemoveLoadIdentifier(uint64_t resourceLoadIdentifier)
     SetDefersLoading(uint64_t resourceLoadIdentifier, bool defers)
+    PrefetchDNS(String hostname)
 
     StartDownload(WebCore::SessionID sessionID, uint64_t downloadID, WebCore::ResourceRequest request)
     ConvertMainResourceLoadToDownload(uint64_t mainResourceLoadIdentifier, uint64_t downloadID, WebCore::ResourceRequest request, WebCore::ResourceResponse response)
index 59ccad6..496f5c0 100644 (file)
@@ -45,6 +45,7 @@
 #include "WebCookieManager.h"
 #include "WebProcessPoolMessages.h"
 #include "WebsiteData.h"
+#include <WebCore/DNS.h>
 #include <WebCore/DiagnosticLoggingClient.h>
 #include <WebCore/Logging.h>
 #include <WebCore/PlatformCookieJar.h>
@@ -529,6 +530,11 @@ void NetworkProcess::processDidResume()
 {
 }
 
+void NetworkProcess::prefetchDNS(const String& hostname)
+{
+    WebCore::prefetchDNS(hostname);
+}
+
 #if !PLATFORM(COCOA)
 void NetworkProcess::initializeProcess(const ChildProcessInitializationParameters&)
 {
index 947e0a2..0e25c38 100644 (file)
@@ -100,6 +100,8 @@ public:
     void clearHSTSCache(WebCore::NetworkStorageSession&, std::chrono::system_clock::time_point modifiedSince);
 #endif
 
+    void prefetchDNS(const String&);
+
 private:
     NetworkProcess();
     ~NetworkProcess();
index cf2696f..344fb22 100644 (file)
@@ -27,7 +27,7 @@
 #include "WebKitPrivate.h"
 #include "WebKitWebExtensionPrivate.h"
 #include "WebKitWebPagePrivate.h"
-#include <WebCore/DNS.h>
+#include "WebProcess.h"
 #include <wtf/HashMap.h>
 #include <wtf/glib/GRefPtr.h>
 
@@ -161,7 +161,7 @@ static void webkitWebExtensionDidReceiveMessage(WebKitWebExtension*, const Strin
 {
     if (messageName == String::fromUTF8("PrefetchDNS")) {
         API::String* hostname = static_cast<API::String*>(message.get(String::fromUTF8("Hostname")));
-        WebCore::prefetchDNS(hostname->string());
+        WebProcess::singleton().prefetchDNS(hostname->string());
     } else
         ASSERT_NOT_REACHED();
 }
index 9ad5019..c7310e9 100644 (file)
@@ -1716,4 +1716,9 @@ void WebFrameLoaderClient::didRequestAutocomplete(PassRefPtr<WebCore::FormState>
 }
 #endif
 
+void WebFrameLoaderClient::prefetchDNS(const String& hostname)
+{
+    WebProcess::singleton().prefetchDNS(hostname);
+}
+
 } // namespace WebKit
index 8f95d05..acb55cf 100644 (file)
@@ -242,6 +242,8 @@ private:
     void contentFilterDidBlockLoad(WebCore::ContentFilterUnblockHandler) override;
 #endif
 
+    void prefetchDNS(const String&) override;
+
     WebFrame* m_frame;
     RefPtr<PluginView> m_pluginView;
     bool m_hasSentResponseToPluginView;
index a1b8906..55daf94 100644 (file)
@@ -50,7 +50,6 @@
 #import "WebProcess.h"
 #import <CoreText/CTFont.h>
 #import <WebCore/Chrome.h>
-#import <WebCore/DNS.h>
 #import <WebCore/DiagnosticLoggingClient.h>
 #import <WebCore/DiagnosticLoggingKeys.h>
 #import <WebCore/Element.h>
@@ -59,6 +58,7 @@
 #import <WebCore/FloatQuad.h>
 #import <WebCore/FocusController.h>
 #import <WebCore/Frame.h>
+#import <WebCore/FrameLoaderClient.h>
 #import <WebCore/FrameView.h>
 #import <WebCore/GeometryUtilities.h>
 #import <WebCore/HTMLElementTypeHelpers.h>
@@ -628,8 +628,10 @@ void WebPage::sendTapHighlightForNodeIfNecessary(uint64_t requestID, Node* node)
     if (!node)
         return;
 
-    if (is<Element>(*node))
-        prefetchDNS(downcast<Element>(*node).absoluteLinkURL().host());
+    if (is<Element>(*node)) {
+        ASSERT(m_page);
+        m_page->mainFrame().loader().client().prefetchDNS(downcast<Element>(*node).absoluteLinkURL().host());
+    }
 
     Vector<FloatQuad> quads;
     if (RenderObject *renderer = node->renderer()) {
index c450560..e2d23b5 100644 (file)
@@ -36,6 +36,7 @@
 #include "EventDispatcher.h"
 #include "InjectedBundle.h"
 #include "Logging.h"
+#include "NetworkConnectionToWebProcessMessages.h"
 #include "PluginProcessConnectionManager.h"
 #include "SessionTracker.h"
 #include "StatisticsData.h"
@@ -67,6 +68,7 @@
 #include <WebCore/ApplicationCacheStorage.h>
 #include <WebCore/AuthenticationChallenge.h>
 #include <WebCore/CrossOriginPreflightResultCache.h>
+#include <WebCore/DNS.h>
 #include <WebCore/FontCache.h>
 #include <WebCore/FontCascade.h>
 #include <WebCore/Frame.h>
@@ -162,6 +164,7 @@ WebProcess::WebProcess()
 #if ENABLE(NETWORK_PROCESS)
     , m_usesNetworkProcess(false)
     , m_webResourceLoadScheduler(new WebResourceLoadScheduler)
+    , m_dnsPrefetchHystereris([this](HysteresisState state) { if (state == HysteresisState::Stopped) m_dnsPrefetchedHosts.clear(); })
 #endif
 #if ENABLE(NETSCAPE_PLUGIN_API)
     , m_pluginProcessConnectionManager(PluginProcessConnectionManager::create())
@@ -1460,4 +1463,23 @@ void WebProcess::setEnabledServices(bool hasImageServices, bool hasSelectionServ
 }
 #endif
 
+void WebProcess::prefetchDNS(const String& hostname)
+{
+    if (hostname.isEmpty())
+        return;
+
+#if ENABLE(NETWORK_PROCESS)
+    if (usesNetworkProcess()) {
+        if (m_dnsPrefetchedHosts.add(hostname).isNewEntry)
+            networkConnection()->connection()->send(Messages::NetworkConnectionToWebProcess::PrefetchDNS(hostname), 0);
+        // The DNS prefetched hosts cache is only to avoid asking for the same hosts too many times
+        // in a very short period of time, producing a lot of IPC traffic. So we clear this cache after
+        // some time of no DNS requests.
+        m_dnsPrefetchHystereris.impulse();
+        return;
+    }
+#endif
+    WebCore::prefetchDNS(hostname);
+}
+
 } // namespace WebKit
index 271c0cd..01d962d 100644 (file)
@@ -37,6 +37,7 @@
 #include "TextCheckerState.h"
 #include "ViewUpdateDispatcher.h"
 #include "VisitedLinkTable.h"
+#include <WebCore/HysteresisActivity.h>
 #include <WebCore/SessionID.h>
 #include <WebCore/Timer.h>
 #include <wtf/Forward.h>
@@ -214,6 +215,8 @@ public:
     bool hasRichContentServices() const { return m_hasRichContentServices; }
 #endif
 
+    void prefetchDNS(const String&);
+
 private:
     WebProcess();
     ~WebProcess();
@@ -360,6 +363,8 @@ private:
     RefPtr<NetworkProcessConnection> m_networkProcessConnection;
     bool m_usesNetworkProcess;
     WebResourceLoadScheduler* m_webResourceLoadScheduler;
+    HashSet<String> m_dnsPrefetchedHosts;
+    WebCore::HysteresisActivity m_dnsPrefetchHystereris;
 #endif
 
 #if ENABLE(DATABASE_PROCESS)