Add LoadState reporting to the mojo proxy resolver.

net/proxy/proxy_resolver.h

Index: net/proxy/proxy_resolver.h
diff --git a/net/proxy/proxy_resolver.h b/net/proxy/proxy_resolver.h
index 721d90f1f1cd15c56814de43a56be7ad9adbdf61..355c368ac26669287098df3cd6a86d30f3148bdc 100644
--- a/net/proxy/proxy_resolver.h
+++ b/net/proxy/proxy_resolver.h
@@ -5,6 +5,7 @@
 #ifndef NET_PROXY_PROXY_RESOLVER_H_
 #define NET_PROXY_PROXY_RESOLVER_H_
 
+#include "base/callback_forward.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string16.h"
@@ -28,6 +29,9 @@ class NET_EXPORT_PRIVATE ProxyResolver {
   // Opaque pointer type, to return a handle to cancel outstanding requests.
   typedef void* RequestHandle;
 
+  using LoadStateChangedCallback =
+      const base::Callback<void(RequestHandle, LoadState)>;
+
   // See |expects_pac_bytes()| for the meaning of |expects_pac_bytes|.
   explicit ProxyResolver(bool expects_pac_bytes)
       : expects_pac_bytes_(expects_pac_bytes) {}