Standardize usage of virtual/override/final specifiers.

components/metrics/gpu/gpu_metrics_provider_unittest.cc

Index: components/metrics/gpu/gpu_metrics_provider_unittest.cc
diff --git a/components/metrics/gpu/gpu_metrics_provider_unittest.cc b/components/metrics/gpu/gpu_metrics_provider_unittest.cc
index 64f957925b2d685cd07d1876eaba3f2ec29dbf99..931b7315dd769f6d237a222429caeacccbc17c6e 100644
--- a/components/metrics/gpu/gpu_metrics_provider_unittest.cc
+++ b/components/metrics/gpu/gpu_metrics_provider_unittest.cc
@@ -42,7 +42,7 @@ class TestGPUMetricsProvider : public GPUMetricsProvider {
 class GPUMetricsProviderTest : public testing::Test {
  public:
   GPUMetricsProviderTest() {}
-  virtual ~GPUMetricsProviderTest() {}
+  ~GPUMetricsProviderTest() override {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GPUMetricsProviderTest);