Add a text/password field count metric for empty username forms.

components/autofill/content/renderer/password_form_conversion_utils.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/autofill/content/renderer/password_form_conversion_utils.h"
 
 #include <vector>
 
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "components/autofill/content/renderer/form_autofill_util.h"
 #include "components/autofill/core/common/form_data_predictions.h"
 #include "components/autofill/core/common/password_form.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/web/WebDocument.h"
 #include "third_party/WebKit/public/web/WebFormControlElement.h"
 #include "third_party/WebKit/public/web/WebInputElement.h"
 #include "third_party/icu/source/i18n/unicode/regex.h"
 
@@ skipping 376 matching lines @@
     password_form->password_value = password_value;
     password_form->password_autocomplete_set = password.autoComplete();
   }
   if (!new_password.isNull()) {
     password_form->new_password_element = new_password.nameForAutofill();
     password_form->new_password_value = new_password.value();
     if (HasAutocompleteAttributeValue(new_password, "new-password"))
       password_form->new_password_marked_by_site = true;
   }
 
+  if (username_element.isNull()) {
+    // To get a better idea on how password forms without a username field
+    // look like, report the total number of text and password fields.
+    UMA_HISTOGRAM_COUNTS_100(
+        "PasswordManager.EmptyUsernames.TextAndPasswordFieldCount",
+        layout_sequence.size());
+  }
+
   password_form->scheme = PasswordForm::SCHEME_HTML;
   password_form->ssl_valid = false;
   password_form->preferred = false;
   password_form->blacklisted_by_user = false;
   password_form->type = PasswordForm::TYPE_MANUAL;
 }
 
 GURL StripAuthAndParams(const GURL& gurl) {
   // We want to keep the path but strip any authentication data, as well as
   // query and ref portions of URL, for the form action and form origin.
@@ skipping 39 matching lines @@
   WebFormElementToFormData(web_form,
                            blink::WebFormControlElement(),
                            EXTRACT_NONE,
                            &password_form->form_data,
                            NULL /* FormFieldData */);
 
   return password_form.Pass();
 }
 
 }  // namespace autofill