Add a Physical Web WebUI for Android

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 b6706c9bd374c18fe4ac86d3f0c29982279977c2..a619666111bf3d56cbd169d3ac93897963a99e02 100644
--- a/components/physical_web/webui/physical_web_base_message_handler.cc
+++ b/components/physical_web/webui/physical_web_base_message_handler.cc
@@ -40,7 +40,7 @@ void PhysicalWebBaseMessageHandler::HandleRequestNearbyURLs(
   for (size_t i = 0; i < metadata->GetSize(); i++) {
     base::DictionaryValue* metadata_item = nullptr;
     metadata->GetDictionary(i, &metadata_item);
-    metadata_item->SetInteger(physical_web_ui::kIndex, i);
+    metadata_item->SetInteger(physical_web_ui::kIndex, static_cast<int>(i));
   }
 
   results.Set(physical_web_ui::kMetadata, metadata.release());