First cut at UI for saving net_logs data into a temporary file on

chrome/browser/net/net_log_logger.cc

Index: chrome/browser/net/net_log_logger.cc
===================================================================
--- chrome/browser/net/net_log_logger.cc	(revision 175049)
+++ chrome/browser/net/net_log_logger.cc	(working copy)
@@ -14,7 +14,7 @@
 #include "base/values.h"
 #include "chrome/browser/ui/webui/net_internals/net_internals_ui.h"
 
-NetLogLogger::NetLogLogger(const FilePath &log_path) {
+NetLogLogger::NetLogLogger(const FilePath &log_path) : net_log_(NULL) {
   if (!log_path.empty()) {
     base::ThreadRestrictions::ScopedAllowIO allow_io;
     FILE* fp = file_util::OpenFile(log_path, "w");
@@ -41,8 +41,15 @@
 
 void NetLogLogger::StartObserving(net::NetLog* net_log) {
   net_log->AddThreadSafeObserver(this, net::NetLog::LOG_ALL_BUT_BYTES);
+  net_log_ = net_log;
 }
 
+void NetLogLogger::StopObserving() {
+  DCHECK(net_log_);
+  net_log_->RemoveThreadSafeObserver(this);
+  net_log_ = NULL;
+}
+
 void NetLogLogger::OnAddEntry(const net::NetLog::Entry& entry) {
   scoped_ptr<Value> value(entry.ToValue());
   // Don't pretty print, so each JSON value occupies a single line, with no