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.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 340 matching lines @@
         base::string16 typed_username_value = username_iterator->second;
         if (!StartsWith(username_value, typed_username_value, false)) {
           // We check that |username_value| was not obtained by autofilling
           // |typed_username_value|. In case when it was, |typed_username_value|
           // is incomplete, so we should leave autofilled value.
           username_value = typed_username_value;
         }
       }
     }
     password_form->username_value = username_value;
+  } else {
+    // To get a better idea on how 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());
   }
 
   WebInputElement password;
   WebInputElement new_password;
   if (!LocateSpecificPasswords(passwords, &password, &new_password))
     return;
 
   password_form->action = GetCanonicalActionForForm(form);
   if (!password_form->action.is_valid())
     return;
@@ skipping 75 matching lines @@
   WebFormElementToFormData(web_form,
                            blink::WebFormControlElement(),
                            EXTRACT_NONE,
                            &password_form->form_data,
                            NULL /* FormFieldData */);
 
   return password_form.Pass();
 }
 
 }  // namespace autofill