[cronet] make startNetLogToFile write to correct file

components/cronet/ios/Cronet.mm

Index: components/cronet/ios/Cronet.mm
diff --git a/components/cronet/ios/Cronet.mm b/components/cronet/ios/Cronet.mm
index 150be2435ff32b9919574f60c8766995eb4f698b..35281d5004365b1661caa239d3e21d3d6b9eeb9d 100644
--- a/components/cronet/ios/Cronet.mm
+++ b/components/cronet/ios/Cronet.mm
@@ -233,10 +233,17 @@ class CronetHttpProtocolHandlerDelegate
   config.protocolClasses = @[ [CRNPauseableHTTPProtocolHandler class] ];
 }
 
-+ (void)startNetLogToFile:(NSString*)fileName logBytes:(BOOL)logBytes {
++ (BOOL)startNetLogToFile:(NSString*)fileName logBytes:(BOOL)logBytes {
   if (gChromeNet.Get().get() && [fileName length]) {
-    gChromeNet.Get()->StartNetLog([fileName UTF8String], logBytes);
+    NSURL* file =
+        [[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory
+                                                 inDomains:NSUserDomainMask]
+            lastObject] URLByAppendingPathComponent:fileName];

[kapishnikov, 2016/11/18 22:17:27]

The documentation of the method implies that absolute path is supported. What
will be the value of |file| if the absolute path is passed?

[lilyhoughton, 2016/11/22 20:48:42]

This is a documentation error.  (Absolute path is supported for the internal cpp
function, but not the Obj-C wrapper).

+    return gChromeNet.Get()->StartNetLog(base::SysNSStringToUTF8([file path]),
+                                         logBytes);
   }
+
+  return NO;
 }
 
 + (void)stopNetLog {