In iossim, use the user's home directory if no override is given.

If no override is given, simHomePath needs to be initialized or iossim
won't know where to find files (e.g. the simulator's sandboxed
system.log)

BUG=None

Review URL: https://codereview.chromium.org/398133002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283643 0039d316-1c4b-4281-b951-d872f2087c98

testing/iossim/iossim.mm

@@ -914,6 +914,8 @@ int main(int argc, char* const argv[]) {
                simHomePath);
       exit(kExitInitializationFailure);
     }
+  } else {
+    simHomePath = NSHomeDirectory();
   }
 
   // Create the config and simulator session.