Add a Dns preresolve interface in //content

content/public/browser/resource_hints.h

Index: content/public/browser/resource_hints.h
diff --git a/content/public/browser/resource_hints.h b/content/public/browser/resource_hints.h
index 94355aef4551170152b6129617fb237512d1e67a..fdb7778374568c282902efdc7a9b488ff09fa52f 100644
--- a/content/public/browser/resource_hints.h
+++ b/content/public/browser/resource_hints.h
@@ -6,13 +6,14 @@
 #define CONTENT_PUBLIC_BROWSER_RESOURCE_HINTS_H_
 
 #include "content/common/content_export.h"
+#include "net/base/completion_callback.h"
 #include "net/http/http_request_info.h"
 #include "url/gurl.h"
 
 class GURL;
 
-namespace net {
-class URLRequestContextGetter;
+namespace content {
+class ResourceContext;
 }
 
 namespace content {
@@ -27,13 +28,19 @@ namespace content {
 // Note: This should only be called on the IO thread, with a valid
 // URLRequestContextGetter.
 CONTENT_EXPORT void PreconnectUrl(
-    net::URLRequestContextGetter* getter,
+    content::ResourceContext* resource_context,
     const GURL& url,
     const GURL& first_party_for_cookies,
     int count,
     bool allow_credentials,
     net::HttpRequestInfo::RequestMotivation motivation);
 
+// Issues a DNS request to |url|. Note that these requests are sent to the host
+// resolver with priority net::IDLE.
+CONTENT_EXPORT int PreresolveUrl(content::ResourceContext* resource_context,
+                                 const GURL& url,
+                                 const net::CompletionCallback& callback);
+
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RESOURCE_HINTS_H_