update_engine: Replace googe::protobuf::Closure with base::Closure

In order to clean up libchromeos, remove chromeos/callback.h and
switch update_engine from using
googe::protobuf::Closure/NewPermanentCallback to base::Closure/Bind

BUG=chromium:406060
TEST=FEATURES=test emerge-link update_engine

Change-Id: I02d222c3f6c9a5bf5177d58e3a25a596348619bf
Reviewed-on: https://chromium-review.googlesource.com/213675
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: David Zeuthen <zeuthen@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/proxy_resolver.cc b/proxy_resolver.cc
index f9905bb..fd233de 100644
--- a/proxy_resolver.cc
+++ b/proxy_resolver.cc
@@ -4,6 +4,8 @@
 
 #include "update_engine/proxy_resolver.h"
 
+#include <base/bind.h>
+
 using std::deque;
 using std::string;
 
@@ -21,11 +23,11 @@
 bool DirectProxyResolver::GetProxiesForUrl(const std::string& url,
                                            ProxiesResolvedFn callback,
                                            void* data) {
-  google::protobuf::Closure* closure = google::protobuf::NewPermanentCallback(
-      this,
+  base::Closure* closure = new base::Closure(base::Bind(
       &DirectProxyResolver::ReturnCallback,
+      base::Unretained(this),
       callback,
-      data);
+      data));
   idle_callback_id_ = g_idle_add_full(
       G_PRIORITY_DEFAULT,
       utils::GlibRunClosure,