Add LoadState reporting to the mojo proxy resolver.

net/base/load_states.h

Index: net/base/load_states.h
diff --git a/net/base/load_states.h b/net/base/load_states.h
index e0915bacbe35b7c5104e8fbf10e7d0970ad60137..aa21c5f8eaa4a7d8a09ebb2025f3740d4996cbab 100644
--- a/net/base/load_states.h
+++ b/net/base/load_states.h
@@ -5,6 +5,7 @@
 #ifndef NET_BASE_LOAD_STATES_H__
 #define NET_BASE_LOAD_STATES_H__
 
+#include "base/callback_forward.h"
 #include "base/strings/string16.h"
 
 namespace net {
@@ -30,6 +31,10 @@ struct LoadStateWithParam {
       : state(state), param(param) {}
 };
 
+template <typename RequestHandle>
+using LoadStateChangedCallback =
+    const base::Callback<void(RequestHandle, LoadState)>;
+
 }  // namespace net
 
 #endif  // NET_BASE_LOAD_STATES_H__