Add link preload as=document support

content/child/web_url_loader_impl.cc

Index: content/child/web_url_loader_impl.cc
diff --git a/content/child/web_url_loader_impl.cc b/content/child/web_url_loader_impl.cc
index 17da0e103519d484dec9df5c4376e17e589aa2f0..ce456205e30a3e54f4f61af9cea63efe592f3870 100644
--- a/content/child/web_url_loader_impl.cc
+++ b/content/child/web_url_loader_impl.cc
@@ -42,6 +42,7 @@
 #include "content/public/common/ssl_status.h"
 #include "net/base/data_url.h"
 #include "net/base/filename_util.h"
+#include "net/base/load_flags.h"
 #include "net/base/net_errors.h"
 #include "net/cert/cert_status_flags.h"
 #include "net/cert/ct_sct_to_string.h"
@@ -449,7 +450,6 @@ void WebURLLoaderImpl::Context::Start(const WebURLRequest& request,
   DCHECK(request_id_ == -1);
   request_ = request;  // Save the request.
   GURL url = request.url();
-
   if (CanHandleDataURLRequestLocally()) {
     if (sync_load_response) {
       // This is a sync load. Do the work now.
@@ -499,6 +499,9 @@ void WebURLLoaderImpl::Context::Start(const WebURLRequest& request,
   request_info.load_flags = GetLoadFlagsForWebURLRequest(request);
   request_info.enable_load_timing = true;
   request_info.enable_upload_progress = request.reportUploadProgress();
+  if (request_.linkPreload())
+      request_info.load_flags |= net::LOAD_PREFETCH;
+
   if (request.getRequestContext() ==
           WebURLRequest::RequestContextXMLHttpRequest &&
       (url.has_username() || url.has_password())) {