Add <link rel=preload> onload support for scripts and styles

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

Index: third_party/WebKit/Source/core/loader/DocumentLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/DocumentLoader.cpp b/third_party/WebKit/Source/core/loader/DocumentLoader.cpp
index f17bb791a94af1a3547f8417069ebef192336a70..d27bff459d171a139a9802ae40a4f470090389c1 100644
--- a/third_party/WebKit/Source/core/loader/DocumentLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/DocumentLoader.cpp
@@ -56,6 +56,7 @@
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/loader/LinkLoader.h"
+#include "core/loader/LinkPreloadResourceClients.h"
 #include "core/loader/ProgressTracker.h"
 #include "core/loader/appcache/ApplicationCacheHost.h"
 #include "core/page/FrameTree.h"
@@ -160,17 +161,23 @@ const KURL& DocumentLoader::url() const
     return m_request.url();
 }
 
-void DocumentLoader::startPreload(Resource::Type type, FetchRequest& request)
+void DocumentLoader::startPreload(Resource::Type type, FetchRequest& request, LinkLoader* linkLoader)

[Nate Chapin, 2016/01/13 23:52:23]

It seems like it would be cleaner to change startPreload() to return a
ResourcePtr<> here and let LinkLoader set up the client.

[Yoav Weiss, 2016/01/14 10:10:02]

Returning things to LinkLoader makes the call from LinkLoader significantly more
complex and forces other call sites of startPreload (HTMLResourcePreloader) to
know the size of LinkPreloadResourceClient. So it's easier to keep setting the
resourceClient here.

OTOH, I did clean up things quite a bit. Let me know if it works, and if not,
I'll change this to return the ResourceClient over.

[Nate Chapin, 2016/01/14 23:10:53]

I don't see how HTMLResourcePreload would need to know anything about
LinkPreloadResourceClient? LinkLoader knows the Resource::Type, so it knows
which (if any) LinkPreloadResourceClient is needed. Suppose
DocumentLoader::startPreload() and LinkLoader.cpp's preloadIfNeeded() are
changed to return a ResourcePtr<Resource>. LinkLoader::loadLink() can check
whether ResourcePtr<Resource> was in fact non-null and create the appropriate
LinkPreloadResourceClient with the Resource. Does that not work for some reason?

 {
     ResourcePtr<Resource> resource;
     switch (type) {
     case Resource::Image:
+        if (linkLoader)
+            linkLoader->setPreloadResourceClient(LinkPreloadImageResourceClient::create(linkLoader));
         resource = ImageResource::fetch(request, fetcher());
         break;
     case Resource::Script:
         resource = ScriptResource::fetch(request, fetcher());
+        if (linkLoader)
+            linkLoader->setPreloadResourceClient(LinkPreloadScriptResourceClient::create(linkLoader));
         break;
     case Resource::CSSStyleSheet:
+        if (linkLoader)
+            linkLoader->setPreloadResourceClient(LinkPreloadStyleResourceClient::create(linkLoader));
         resource = CSSStyleSheetResource::fetch(request, fetcher());
         break;
     case Resource::Font:
@@ -192,8 +199,12 @@ void DocumentLoader::startPreload(Resource::Type type, FetchRequest& request)
         ASSERT_NOT_REACHED();
     }
 
-    if (resource)
-        fetcher()->preloadStarted(resource.get());
+    if (!resource)
+        return;
+
+    if (linkLoader && linkLoader->preloadResourceClient())
+        linkLoader->preloadResourceClient()->callSetResource(resource.get());
+    fetcher()->preloadStarted(resource.get());
 }
 
 void DocumentLoader::didChangePerformanceTiming()