Move net-export thread-hopping code into NetLogFileWriter and add IO polled data.

net/log/write_to_file_net_log_observer.cc

Index: net/log/write_to_file_net_log_observer.cc
diff --git a/net/log/write_to_file_net_log_observer.cc b/net/log/write_to_file_net_log_observer.cc
index 5470ebbcd44d2d880fe9b1a4d8c387ea5db9f7f2..0c79ea3387146851fd923cc934fb85a547ab9ca7 100644
--- a/net/log/write_to_file_net_log_observer.cc
+++ b/net/log/write_to_file_net_log_observer.cc
@@ -67,21 +67,16 @@ void WriteToFileNetLogObserver::StartObserving(
   net_log->DeprecatedAddObserver(this, capture_mode_);
 }
 
-void WriteToFileNetLogObserver::StopObserving(
-    URLRequestContext* url_request_context) {
+void WriteToFileNetLogObserver::StopObserving(base::Value* polled_data) {
   net_log()->DeprecatedRemoveObserver(this);
 
   // End events array.
   fprintf(file_.get(), "]");
 
-  // Write state of the URLRequestContext when logging stopped.
-  if (url_request_context) {
-    DCHECK(url_request_context->CalledOnValidThread());
-
+  if (polled_data) {
     std::string json;
-    base::JSONWriter::Write(
-        *GetNetInfo(url_request_context, NET_INFO_ALL_SOURCES), &json);
-    fprintf(file_.get(), ",\"tabInfo\": %s\n", json.c_str());
+    base::JSONWriter::Write(*polled_data, &json);
+    fprintf(file_.get(), ",\"polledData\": %s\n", json.c_str());
   }
   fprintf(file_.get(), "}");