[cronet] make startNetLogToFile write to correct file

components/cronet/ios/Cronet.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <Foundation/Foundation.h>
 
 #include "bidirectional_stream_c.h"
 
 // TODO(mef): Remove this header after transition to bidirectional_stream_c.h
 // See crbug.com/650462 for details.
@@ skipping 61 matching lines @@
 // This method must be called after |start|.
 + (void)unregisterHttpProtocolHandler;
 
 // Installs Cronet into NSURLSessionConfiguration so that all
 // NSURLSessions created with this configuration will use the Cronet stack.
 // Note that all Cronet settings are global and are shared between
 // all NSURLSessions & NSURLConnections that use the Cronet stack.
 // This method must be called after |start|.
 + (void)installIntoSessionConfiguration:(NSURLSessionConfiguration*)config;
 
-// Starts net-internals logging to a file named |fileName| in the application
-// temporary directory. |fileName| must not be empty. Log level is determined
-// by |logBytes| - if YES then LOG_ALL otherwise LOG_ALL_BUT_BYTES. If the file
-// exists it is truncated before starting. If actively logging the call is
-// ignored.
-+ (void)startNetLogToFile:(NSString*)fileName logBytes:(BOOL)logBytes;
+// Returns the absolute path that startNetLogToFile:fileName will actually
+// write to.
++ (NSString*)getNetLogPathForFile:(NSString*)fileName;
+
+// Starts net-internals logging to a file named |fileName|. Where fileName is
+// relative to the application documents directory. |fileName| must not be
+// empty. Log level is determined by |logBytes| - if YES then LOG_ALL otherwise
+// LOG_ALL_BUT_BYTES. If the file exists it is truncated before starting. If
+// actively logging the call is ignored.
++ (BOOL)startNetLogToFile:(NSString*)fileName logBytes:(BOOL)logBytes;
 
 // Stop net-internals logging and flush file to disk. If a logging session is
 // not in progress this call is ignored.
 + (void)stopNetLog;
 
 // Returns the full user-agent that the stack uses.
 // This is the exact string servers will see.
 + (NSString*)getUserAgent;
 
 // Get a pointer to global instance of cronet_engine for GRPC C API.
@@ skipping 10 matching lines @@
 
 // Sets Host Resolver Rules for testing.
 // This method must be called after |start| has been called.
 + (void)setHostResolverRulesForTesting:(NSString*)hostResolverRulesForTesting;
 
 // Enables TestCertVerifier which accepts all certificates for testing.
 // This method only has any effect before |start| is called.
 + (void)enableTestCertVerifierForTesting;
 
 @end