Add instrumentation for password autofill and Credential Manager API user flows.

components/password_manager/core/browser/credential_manager_pending_request_task.cc

Index: components/password_manager/core/browser/credential_manager_pending_request_task.cc
diff --git a/components/password_manager/core/browser/credential_manager_pending_request_task.cc b/components/password_manager/core/browser/credential_manager_pending_request_task.cc
index dc995b0ad2a013c860242e2081edc6c6166207f9..ed8c3e7b432be5835da747af3eb21a4ca35bb4a1 100644
--- a/components/password_manager/core/browser/credential_manager_pending_request_task.cc
+++ b/components/password_manager/core/browser/credential_manager_pending_request_task.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 #include <utility>
 
+#include "base/metrics/user_metrics.h"
 #include "components/autofill/core/common/password_form.h"
 #include "components/password_manager/core/browser/affiliated_match_helper.h"
 #include "components/password_manager/core/browser/password_bubble_experiment.h"
@@ -124,6 +125,8 @@ void CredentialManagerPendingRequestTask::OnGetPasswordStoreResults(
   local_results.erase(begin_empty, local_results.end());
 
   if ((local_results.empty() && federated_results.empty())) {
+    base::RecordAction(
+        base::UserMetricsAction("Credential_Manager_Get_EmptyStore"));
     delegate_->SendCredential(send_callback_, CredentialInfo());
     return;
   }
@@ -145,6 +148,8 @@ void CredentialManagerPendingRequestTask::OnGetPasswordStoreResults(
                             : CredentialType::CREDENTIAL_TYPE_FEDERATED);
     delegate_->client()->NotifyUserAutoSignin(std::move(local_results),
                                               origin_);
+    base::RecordAction(
+        base::UserMetricsAction("Credential_Manager_Autosignin"));
     delegate_->SendCredential(send_callback_, info);
     return;
   }