[PhysicalWeb] Add physical_web namespace.

ios/chrome/test/testing_application_context.mm

Index: ios/chrome/test/testing_application_context.mm
diff --git a/ios/chrome/test/testing_application_context.mm b/ios/chrome/test/testing_application_context.mm
index e03bd89ac4fcd032a5bc6f9efcdeb53adafee28e..162f02344ec1bb972d460a6c929ee9d672d39982 100644
--- a/ios/chrome/test/testing_application_context.mm
+++ b/ios/chrome/test/testing_application_context.mm
@@ -155,7 +155,8 @@ CRLSetFetcher* TestingApplicationContext::GetCRLSetFetcher() {
   return nullptr;
 }
 
-PhysicalWebDataSource* TestingApplicationContext::GetPhysicalWebDataSource() {
+physical_web::PhysicalWebDataSource*
+TestingApplicationContext::GetPhysicalWebDataSource() {
   DCHECK(thread_checker_.CalledOnValidThread());
   return nullptr;
 }