Add an IPC for PNaCl to check if the session is incognito, before deciding

ppapi/native_client/src/trusted/plugin/local_temp_file.h

Index: ppapi/native_client/src/trusted/plugin/local_temp_file.h
diff --git a/ppapi/native_client/src/trusted/plugin/local_temp_file.h b/ppapi/native_client/src/trusted/plugin/local_temp_file.h
index 3e3858d181afe477f6da353992a48ad7814b4bf4..51d2095f1c9ecb17d92395e436c4e7dd34cafdd3 100644
--- a/ppapi/native_client/src/trusted/plugin/local_temp_file.h
+++ b/ppapi/native_client/src/trusted/plugin/local_temp_file.h
@@ -82,7 +82,7 @@ class LocalTempFile {
   const nacl::string identifier() const {
     return nacl::string(reinterpret_cast<const char*>(identifier_));
   }
-  const pp::FileIO& write_file_io() const { return *write_io_; }
+  pp::FileIO* write_file_io() const { return write_io_.get(); }
 
  private:
   NACL_DISALLOW_COPY_AND_ASSIGN(LocalTempFile);