Update Physical Web WebUI to show new results automatically

components/physical_web/webui/physical_web_base_message_handler.cc

Index: components/physical_web/webui/physical_web_base_message_handler.cc
diff --git a/components/physical_web/webui/physical_web_base_message_handler.cc b/components/physical_web/webui/physical_web_base_message_handler.cc
index 68aeca7791e14c274f27283fd78eb9726cfa9b22..75ed1a550411778df40334d1b53a10ef0f4a4f85 100644
--- a/components/physical_web/webui/physical_web_base_message_handler.cc
+++ b/components/physical_web/webui/physical_web_base_message_handler.cc
@@ -13,9 +13,26 @@
 
 namespace physical_web_ui {
 
-PhysicalWebBaseMessageHandler::PhysicalWebBaseMessageHandler() {}
+PhysicalWebBaseMessageHandler::PhysicalWebBaseMessageHandler()
+  : data_source_(nullptr) {}
 
-PhysicalWebBaseMessageHandler::~PhysicalWebBaseMessageHandler() = default;
+PhysicalWebBaseMessageHandler::~PhysicalWebBaseMessageHandler() {
+  if (data_source_)
+    data_source_->UnregisterListener(this);
+}
+
+void PhysicalWebBaseMessageHandler::OnFound(const GURL& url) {
+  HandleRequestNearbyURLs(nullptr);
+}
+
+void PhysicalWebBaseMessageHandler::OnLost(const GURL& url) {
+  // do nothing
+}
+
+void PhysicalWebBaseMessageHandler::OnDistanceChanged(
+    const GURL& url, double distance_estimate) {
+  // do nothing
+}
 
 void PhysicalWebBaseMessageHandler::RegisterMessages() {
   RegisterMessageCallback(
@@ -27,6 +44,10 @@ void PhysicalWebBaseMessageHandler::RegisterMessages() {
       base::BindRepeating(
           &PhysicalWebBaseMessageHandler::HandlePhysicalWebItemClicked,
           base::Unretained(this)));
+
+  data_source_ = GetPhysicalWebDataSource();
+  if (data_source_)
+    data_source_->RegisterListener(this);
 }
 
 void PhysicalWebBaseMessageHandler::HandleRequestNearbyURLs(
@@ -36,9 +57,19 @@ void PhysicalWebBaseMessageHandler::HandleRequestNearbyURLs(
   std::unique_ptr<physical_web::MetadataList> metadata_list =
       GetPhysicalWebDataSource()->GetMetadataList();
 
+  // Append new metadata at the end of the list.
+  for (const auto& metadata_list_item : *metadata_list) {
+    const std::string& group_id = metadata_list_item.group_id;
+    if (metadata_map_.find(group_id) == metadata_map_.end()) {
+      ordered_group_ids_.push_back(group_id);
+      metadata_map_.emplace(group_id, metadata_list_item);
+    }
+  }
+
   auto metadata = base::MakeUnique<base::ListValue>();
   int index = 0;
-  for (const auto& metadata_list_item : *metadata_list) {
+  for (const auto& group_id : ordered_group_ids_) {
+    auto metadata_list_item = metadata_map_[group_id];
     auto metadata_item = base::MakeUnique<base::DictionaryValue>();
     metadata_item->SetString(physical_web_ui::kResolvedUrl,
                              metadata_list_item.resolved_url.spec());