Handled nullptr argument in WaitForExit() and WaitForExitWithTimeout() methods.

base/process/process_win.cc

Index: base/process/process_win.cc
diff --git a/base/process/process_win.cc b/base/process/process_win.cc
index 0d312a3599088eabf4bc2043a5f875b6d1f9d019..e2dfcdf79fd8b898c48ab84c1bbc6309d90bfde7 100644
--- a/base/process/process_win.cc
+++ b/base/process/process_win.cc
@@ -153,8 +153,8 @@ bool Process::WaitForExitWithTimeout(TimeDelta timeout, int* exit_code) {
   DWORD temp_code;  // Don't clobber out-parameters in case of failure.
   if (!::GetExitCodeProcess(Handle(), &temp_code))
     return false;
-
-  *exit_code = temp_code;
+  if (exit_code)
+    *exit_code = temp_code;
   return true;
 }