DNS: Let requests specify a callback for future cache hits

net/dns/host_cache_unittest.cc

Index: net/dns/host_cache_unittest.cc
diff --git a/net/dns/host_cache_unittest.cc b/net/dns/host_cache_unittest.cc
index c34627b1696a82a88e6aab1bc0a61e7c75758844..00ec78258c00991efa4af103aba5565608924129 100644
--- a/net/dns/host_cache_unittest.cc
+++ b/net/dns/host_cache_unittest.cc
@@ -329,6 +329,57 @@ TEST(HostCacheTest, Evict) {
   EXPECT_TRUE(cache.Lookup(key3, now));
 }
 
+void TestEvictionCallback(int* evict_count,
+                          HostCache::Key* key_out,
+                          const HostCache::Key& key,
+                          const HostCache::Entry& entry) {
+  ++*evict_count;
+  *key_out = key;
+}
+
+// Try to add too many entries to cache; it should evict the one with the oldest
+// expiration time.
+TEST(HostCacheTest, EvictWithCallback) {
+  HostCache cache(2);
+
+  int evict_count = 0;
+  HostCache::Key evicted_key = Key("nothingevicted.com");
+  cache.set_eviction_callback(
+      base::Bind(&TestEvictionCallback, &evict_count, &evicted_key));
+
+  base::TimeTicks now;
+
+  HostCache::Key key1 = Key("foobar.com");
+  HostCache::Key key2 = Key("foobar2.com");
+  HostCache::Key key3 = Key("foobar3.com");
+  HostCache::Entry entry = HostCache::Entry(OK, AddressList());
+
+  EXPECT_EQ(0u, cache.size());
+  EXPECT_FALSE(cache.Lookup(key1, now));
+  EXPECT_FALSE(cache.Lookup(key2, now));
+  EXPECT_FALSE(cache.Lookup(key3, now));
+
+  // |key1| expires in 10 seconds, but |key2| in just 5.
+  cache.Set(key1, entry, now, base::TimeDelta::FromSeconds(10));
+  cache.Set(key2, entry, now, base::TimeDelta::FromSeconds(5));
+  EXPECT_EQ(2u, cache.size());
+  EXPECT_TRUE(cache.Lookup(key1, now));
+  EXPECT_TRUE(cache.Lookup(key2, now));
+  EXPECT_FALSE(cache.Lookup(key3, now));
+
+  EXPECT_EQ(0, evict_count);
+
+  // |key2| should be chosen for eviction, since it expires sooner.
+  cache.Set(key3, entry, now, base::TimeDelta::FromSeconds(10));
+  EXPECT_EQ(2u, cache.size());
+  EXPECT_TRUE(cache.Lookup(key1, now));
+  EXPECT_FALSE(cache.Lookup(key2, now));
+  EXPECT_TRUE(cache.Lookup(key3, now));
+
+  EXPECT_EQ(1, evict_count);
+  EXPECT_EQ(key2.hostname, evicted_key.hostname);
+}
+
 // Try to retrieve stale entries from the cache. They should be returned by
 // |LookupStale()| but not |Lookup()|, with correct |EntryStaleness| data.
 TEST(HostCacheTest, Stale) {