Convert //chrome/browser/extensions from scoped_ptr to std::unique_ptr

chrome/browser/extensions/api/metrics_private/metrics_apitest.cc

Index: chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
diff --git a/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc b/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
index 3160400b6dc7f7b0450d25fe5a1a05274211cf4d..83b6a7fad5c62f1286434e1ebf4d1e9e51961bc4 100644
--- a/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
+++ b/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
@@ -107,7 +107,7 @@ void ValidateHistograms(const RecordedHistogram* recorded,
     for (j = 0; j < histograms.size(); ++j) {
       base::HistogramBase* histogram(histograms[j]);
       if (r.name == histogram->histogram_name()) {
-        scoped_ptr<base::HistogramSamples> snapshot =
+        std::unique_ptr<base::HistogramSamples> snapshot =
             histogram->SnapshotSamples();
         base::HistogramBase::Count sample_count = snapshot->TotalCount();
         EXPECT_EQ(r.count, sample_count);