Add physical_web namespace

ios/chrome/browser/physical_web/create_physical_web_data_source.mm

Index: ios/chrome/browser/physical_web/create_physical_web_data_source.mm
diff --git a/ios/chrome/browser/physical_web/create_physical_web_data_source.mm b/ios/chrome/browser/physical_web/create_physical_web_data_source.mm
index 307728e91fc5343cac2b6a8579f5a36d6ae6bba2..8ea22fab5cac578cc24743bd4deb33fa397835a2 100644
--- a/ios/chrome/browser/physical_web/create_physical_web_data_source.mm
+++ b/ios/chrome/browser/physical_web/create_physical_web_data_source.mm
@@ -7,6 +7,9 @@
 #include "base/memory/ptr_util.h"
 #import "ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.h"
 
-std::unique_ptr<PhysicalWebDataSource> CreateIOSChromePhysicalWebDataSource() {
-  return base::MakeUnique<IOSChromePhysicalWebDataSource>();
+std::unique_ptr<physical_web::PhysicalWebDataSource>
+CreateIOSChromePhysicalWebDataSource() {
+  std::unique_ptr<physical_web::PhysicalWebDataSource> datasource =
+      base::MakeUnique<IOSChromePhysicalWebDataSource>();
+  return datasource;
 }