update_engine: fix -Winconsistent-missing-override warning

BUG=chromium:453566
TEST=FEATURES="test" emerge-amd64-generic update_engine

Change-Id: Icf889d01021993e6b3175b3a15efe82069d2d2fc
Reviewed-on: https://chromium-review.googlesource.com/244411
Reviewed-by: Alex Deymo <deymo@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Commit-Queue: Yunlian Jiang <yunlian@chromium.org>
diff --git a/update_manager/real_random_provider.cc b/update_manager/real_random_provider.cc
index add26e5..2aa8d57 100644
--- a/update_manager/real_random_provider.cc
+++ b/update_manager/real_random_provider.cc
@@ -37,8 +37,8 @@
   ~RandomSeedVariable() override {}
 
  protected:
-  virtual const uint64_t* GetValue(base::TimeDelta /* timeout */,
-                                   string* errmsg) {
+  const uint64_t* GetValue(base::TimeDelta /* timeout */,
+                           string* errmsg) override {
     uint64_t result;
     // Aliasing via char pointer abides by the C/C++ strict-aliasing rules.
     char* const buf = reinterpret_cast<char*>(&result);