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..26dcfa35ccf8abf85c1397de3ed8516819d84bb4 100644
--- a/content/public/browser/resource_hints.h
+++ b/content/public/browser/resource_hints.h
@@ -6,6 +6,7 @@
 #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"
 
@@ -17,6 +18,10 @@ class URLRequestContextGetter;
 
 namespace content {
 
+// TODO(csharrison): A cleaner interface woulbe to use ResourceContext instead
+// of URLRequestContextGetter for these functions. The predictor will need to be
+// modified for this purpose to guarantee lifetime semantics.
+
 // A Preconnect instance maintains state while a TCP/IP connection is made, and
 // then released into the pool of available connections for future use.
 
@@ -34,6 +39,12 @@ CONTENT_EXPORT void PreconnectUrl(
     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(net::URLRequestContextGetter* getter,
+                                 const GURL& url,
+                                 const net::CompletionCallback& callback);
+
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RESOURCE_HINTS_H_