Remove a CHECK from single_tree_tracker_unittest.cc

CHECK should not be used in tests. This test uses a net::MockCachingHostResolver, so the HostCache
argument that was being checked should never be null.

Change-Id: Ibaa7051c404037089fb010a0ed11ee8775c70277
Reviewed-on: https://chromium-review.googlesource.com/823962Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Commit-Queue: Rob Percival <robpercival@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523779}

components/certificate_transparency/single_tree_tracker_unittest.cc

@@ -174,10 +174,9 @@ void AddCacheEntry(net::HostCache* cache,
                    const std::string& hostname,
                    net::HostCache::Entry::Source source,
                    base::TimeDelta ttl) {
-  CHECK(cache);
-  const net::HostCache::Key key(hostname, net::ADDRESS_FAMILY_UNSPECIFIED, 0);
-  const net::HostCache::Entry entry(net::OK, net::AddressList(), source);
-  cache->Set(key, entry, base::TimeTicks::Now(), ttl);
+  cache->Set(net::HostCache::Key(hostname, net::ADDRESS_FAMILY_UNSPECIFIED, 0),
+             net::HostCache::Entry(net::OK, net::AddressList(), source),
+             base::TimeTicks::Now(), ttl);
 }
 
 }  // namespace