Report Precache.TimeSinceLastPrecache

components/precache/core/precache_database_unittest.cc

Index: components/precache/core/precache_database_unittest.cc
diff --git a/components/precache/core/precache_database_unittest.cc b/components/precache/core/precache_database_unittest.cc
index 3f9253c744af757c3272e89fc7f0eceeb8b34204..e03a7c4836196b964021f7ffa69cb1166fa645a2 100644
--- a/components/precache/core/precache_database_unittest.cc
+++ b/components/precache/core/precache_database_unittest.cc
@@ -381,6 +381,34 @@ TEST_F(PrecacheDatabaseTest, SampleInteraction) {
               ElementsAre(Bucket(kSize1, 1)));
 }
 
+TEST_F(PrecacheDatabaseTest, LastPrecacheTimestamp) {
+  // So that it starts recording TimeSinceLastPrecache.
+  const base::Time kStartTime =
+      base::Time() + base::TimeDelta::FromSeconds(100);
+  precache_database_->SetLastPrecacheTimestamp(kStartTime);
+
+  RecordPrecacheFromNetwork(kURL, kLatency, kStartTime, kSize);
+  RecordPrecacheFromNetwork(kURL, kLatency, kStartTime, kSize);
+  RecordPrecacheFromNetwork(kURL, kLatency, kStartTime, kSize);
+  RecordPrecacheFromNetwork(kURL, kLatency, kStartTime, kSize);
+
+  EXPECT_THAT(histograms_.GetAllSamples("Precache.TimeSinceLastPrecache"),
+              ElementsAre());
+
+  const base::Time kTimeA = kStartTime + base::TimeDelta::FromSeconds(7);
+  const base::Time kTimeB = kStartTime + base::TimeDelta::FromSeconds(11);
+
+  RecordFetchFromCacheCellular(kURL, kTimeA, kSize);
+  RecordFetchFromCacheCellular(kURL, kTimeA, kSize);
+  RecordFetchFromNetworkCellular(kURL, kLatency, kTimeB, kSize);
+  RecordFetchFromNetworkCellular(kURL, kLatency, kTimeB, kSize);
+  RecordFetchFromCacheCellular(kURL, kTimeB, kSize);
+
+  EXPECT_THAT(histograms_.GetAllSamples("Precache.TimeSinceLastPrecache"),
+              // Buckets are in milliseconds.
+              ElementsAre(Bucket(5961, 2), Bucket(10000, 3)));
+}
+
 }  // namespace
 
 }  // namespace precache