Add a metric for autofilled Android credentials.

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 f956cff2a0b6455d02a7125daacbc0244449c501..17159469bc9fa5467c59bb0e0264aae1660d2084 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -27498,6 +27498,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PasswordManager.OfferedToFillAndroidCredentials"
+    enum="PasswordManagerFillAndroidCredentials">
+  <owner>msramek@chromium.org</owner>
+  <owner>engedy@chromium.org</owner>
+  <summary>
+    When offering to fill the username and password, whether at least one of the
+    credentials in the dropdown come from an Android app.

[vabr (Chromium), 2015/06/18 13:21:47]

Please double-check if it should be "come" or "comes". It is 3rd person
singular, but perhaps not indicative. I give up. :)

[msramek, 2015/06/18 14:22:27]

Sorry, I just messed up. It's not conjunctive or anything.

I was referring to "one pair of username and password" as "one credentials",
which itself doesn't make much sense. After reading
http://english.stackexchange.com/questions/252073/which-is-correct-credential...,
I decided to just use the singular "credential" for everyone's sanity.

[vabr (Chromium), 2015/06/18 15:59:03]

Acknowledged.

+  </summary>
+</histogram>
+
 <histogram name="PasswordManager.OsPasswordStatus"
     enum="PasswordManagerOsPasswordStatus">
   <owner>dubroy@chromium.org</owner>
@@ -62121,6 +62131,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="A password change form"/>
 </enum>
 
+<enum name="PasswordManagerFillAndroidCredentials" type="int">
+  <int value="0" label="Credentials NOT from Android"/>

[vabr (Chromium), 2015/06/18 13:21:47]

Would
"No credentials from Android"
"At least one credential from Android"
be more precise?

[msramek, 2015/06/18 14:22:27]

Ah, thanks. I wanted to use very general wording, so I can reuse this enum for
more metrics, and didn't realize that it no longer works for this one.

Since this enum is now tied specifically to this particular metrics, I again
changed the naming to contain the word "offer".

[vabr (Chromium), 2015/06/18 15:59:03]

Acknowledged.

+  <int value="1" label="Credentials from Android"/>
+</enum>
+
 <enum name="PasswordManagerOsPasswordStatus" type="int">
   <int value="0" label="Unknown"/>
   <int value="1" label="Unsupported platform"/>