Add OVERRIDE to chrome/common/ and nacl/.

chrome/common/metrics_helpers.h

Index: chrome/common/metrics_helpers.h
diff --git a/chrome/common/metrics_helpers.h b/chrome/common/metrics_helpers.h
index 65c111d88e60110a7abb6b8b8f93a6f987f948e7..85eed9c22998c396b10540444074fe667ff8586a 100644
--- a/chrome/common/metrics_helpers.h
+++ b/chrome/common/metrics_helpers.h
@@ -236,10 +236,10 @@ class MetricsServiceBase : public HistogramSender {
   // HistogramSender interface (override) methods.
   virtual void TransmitHistogramDelta(
       const base::Histogram& histogram,
-      const base::Histogram::SampleSet& snapshot);
-  virtual void InconsistencyDetected(int problem);
-  virtual void UniqueInconsistencyDetected(int problem);
-  virtual void SnapshotProblemResolved(int amount);
+      const base::Histogram::SampleSet& snapshot) OVERRIDE;
+  virtual void InconsistencyDetected(int problem) OVERRIDE;
+  virtual void UniqueInconsistencyDetected(int problem) OVERRIDE;
+  virtual void SnapshotProblemResolved(int amount) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsServiceBase);
 };