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

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index ab123224f2860a2b8f78e77c1057028c1e7c0773..439751e7265f36fb2e3aadefa663e52bf6cde894 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -25700,6 +25700,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="PasswordManager.EmptyUsernames.TextAndPasswordFieldCount">
+  <owner>msramek@chromium.org</owner>
+  <owner>vasilii@chromium.org</owner>
+  <summary>
+    The total number of text and password fields for forms that do not have a
+    username field.

[vabr (Chromium), 2015/05/12 11:06:11]

Please also say that only forms with at least one password field are included in
the count.

[msramek, 2015/05/12 11:27:03]

I changed "forms" to "password forms", is that clear enough?

[vabr (Chromium), 2015/05/12 11:33:58]

Acknowledged.

+  </summary>
+</histogram>
+
 <histogram name="PasswordManager.EmptyUsernames.WithoutCorrespondingNonempty">
   <owner>msramek@chromium.org</owner>
   <owner>vasilii@chromium.org</owner>