Add a network quality cache observer

net/nqe/network_quality_store.cc

Index: net/nqe/network_quality_store.cc
diff --git a/net/nqe/network_quality_store.cc b/net/nqe/network_quality_store.cc
index 4f744917070899451e83b64ae507b4ad0527fb0d..7a1c253bdbaf7af91de5f69f800dc46c11e56c5c 100644
--- a/net/nqe/network_quality_store.cc
+++ b/net/nqe/network_quality_store.cc
@@ -59,6 +59,10 @@ void NetworkQualityStore::Add(
       std::make_pair(network_id, cached_network_quality));
   DCHECK_LE(cached_network_qualities_.size(),
             static_cast<size_t>(kMaximumNetworkQualityCacheSize));
+
+  FOR_EACH_OBSERVER(
+      NetworkQualitiesCacheObserver, network_qualities_cache_observer_list_,
+      OnChangeInCachedNetworkQuality(network_id, cached_network_quality));
 }
 
 bool NetworkQualityStore::GetById(
@@ -76,6 +80,20 @@ bool NetworkQualityStore::GetById(
   return true;
 }
 
+void NetworkQualityStore::AddNetworkQualitiesCacheObserver(
+    nqe::internal::NetworkQualityStore::NetworkQualitiesCacheObserver*
+        observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  network_qualities_cache_observer_list_.AddObserver(observer);
+}
+
+void NetworkQualityStore::RemoveNetworkQualitiesCacheObserver(
+    nqe::internal::NetworkQualityStore::NetworkQualitiesCacheObserver*
+        observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  network_qualities_cache_observer_list_.RemoveObserver(observer);
+}
+
 }  // namespace internal
 
 }  // namespace nqe