Standardize usage of virtual/override/final specifiers.

chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc

Index: chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc
diff --git a/chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc b/chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc
index 58ee9c3aa0f114db6093b4b1125fe837c1c6a3f9..5245ffb395d60f6542d1dea4c3ee91cddc720b5e 100644
--- a/chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc
+++ b/chrome/browser/sync/test/integration/sync_exponential_backoff_test.cc
@@ -21,7 +21,7 @@ using sync_integration_test_util::AwaitCommitActivityCompletion;
 class SyncExponentialBackoffTest : public SyncTest {
  public:
   SyncExponentialBackoffTest() : SyncTest(SINGLE_CLIENT) {}
-  virtual ~SyncExponentialBackoffTest() {}
+  ~SyncExponentialBackoffTest() override {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncExponentialBackoffTest);