Track empty username and password in PasswordStore.

Having both username and password empty is incorrect. We should find out where they come from.

BUG=404012

Review URL: https://codereview.chromium.org/514573002

Cr-Commit-Position: refs/heads/master@{#292135}

components/password_manager/core/browser/password_store.cc

@@ -5,6 +5,7 @@
 #include "components/password_manager/core/browser/password_store.h"
 
 #include "base/bind.h"
+#include "base/debug/dump_without_crashing.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ -35,6 +36,12 @@ void MaybeCallConsumerCallback(base::WeakPtr<PasswordStoreConsumer> consumer,
     STLDeleteElements(result.get());
 }
 
+// http://crbug.com/404012. Let's see where the empty fields come from.
+void CheckForEmptyUsernameAndPassword(const PasswordForm& form) {
+  if (form.username_value.empty() && form.password_value.empty())
+    base::debug::DumpWithoutCrashing();
+}
+
 }  // namespace
 
 PasswordStore::GetLoginsRequest::GetLoginsRequest(
@@ -88,12 +95,14 @@ bool PasswordStore::Init(const syncer::SyncableService::StartSyncFlare& flare,
 }
 
 void PasswordStore::AddLogin(const PasswordForm& form) {
+  CheckForEmptyUsernameAndPassword(form);
   ScheduleTask(
       base::Bind(&PasswordStore::WrapModificationTask, this,
                  base::Bind(&PasswordStore::AddLoginImpl, this, form)));
 }
 
 void PasswordStore::UpdateLogin(const PasswordForm& form) {
+  CheckForEmptyUsernameAndPassword(form);
   ScheduleTask(
       base::Bind(&PasswordStore::WrapModificationTask, this,
                  base::Bind(&PasswordStore::UpdateLoginImpl, this, form)));