[cronet] make startNetLogToFile write to correct file

components/cronet/ios/cronet_environment.h

Index: components/cronet/ios/cronet_environment.h
diff --git a/components/cronet/ios/cronet_environment.h b/components/cronet/ios/cronet_environment.h
index 6afde9cb6236346fda0a17db616f6ee6375e1e88..72aa23dc38ebcf8046ab51dafa841b41a5357055 100644
--- a/components/cronet/ios/cronet_environment.h
+++ b/components/cronet/ios/cronet_environment.h
@@ -60,7 +60,7 @@ class CronetEnvironment {
 
   // Creates a new net log (overwrites existing file with this name). If
   // actively logging, this call is ignored.
-  void StartNetLog(base::FilePath::StringType file_name, bool log_bytes);
+  bool StartNetLog(base::FilePath::StringType file_name, bool log_bytes);
   // Stops logging and flushes file. If not currently logging this call is
   // ignored.
   void StopNetLog();
@@ -111,8 +111,7 @@ class CronetEnvironment {
                                     const base::Closure& task);
 
   // Helper methods that start/stop net logging on the network thread.
-  void StartNetLogOnNetworkThread(const base::FilePath::StringType& file_name,
-                                  bool log_bytes);
+  void StartNetLogOnNetworkThread(base::ScopedFILE file, bool log_bytes);
   void StopNetLogOnNetworkThread(base::WaitableEvent* log_stopped_event);
 
   // Returns the HttpNetworkSession object from the passed in