Update {virtual,override} to follow C++11 style in components.

components/invalidation/unacked_invalidation_set_test_util.cc

Index: components/invalidation/unacked_invalidation_set_test_util.cc
diff --git a/components/invalidation/unacked_invalidation_set_test_util.cc b/components/invalidation/unacked_invalidation_set_test_util.cc
index 15bf7fd0e589a5dd95b9400231bdb6324a348d52..165df6eca06a8e87bc94f85df780e39afc01434e 100644
--- a/components/invalidation/unacked_invalidation_set_test_util.cc
+++ b/components/invalidation/unacked_invalidation_set_test_util.cc
@@ -28,11 +28,11 @@ class UnackedInvalidationSetEqMatcher
   explicit UnackedInvalidationSetEqMatcher(
       const UnackedInvalidationSet& expected);
 
-  virtual bool MatchAndExplain(
+  bool MatchAndExplain(
       const UnackedInvalidationSet& actual,
       MatchResultListener* listener) const override;
-  virtual void DescribeTo(::std::ostream* os) const override;
-  virtual void DescribeNegationTo(::std::ostream* os) const override;
+  void DescribeTo(::std::ostream* os) const override;
+  void DescribeNegationTo(::std::ostream* os) const override;
 
  private:
   const UnackedInvalidationSet expected_;