Create a mechanism for reporting rappor metrics from non-UMA

tools/metrics/rappor/rappor.xml

 <!--
 Copyright 2014 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.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome rappor metrics
 along with a detailed description for each histogram. See the design doc at
 http://www.chromium.org/developers/design-documents/rappor
 for a description of rappor metrics.
 
 TODO(holte): Add validation and pretty printing scripts.
 -->
 
 <rappor-configuration>
 
+<!--
+Parameters that rappor metrics can be collected with.  This list should be
+kept in sync with parameter type definitions in
+components/rappor/rappor_service.cc.

[Alexei Svitkine (slow), 2014/11/03 21:48:21]

Can you also file a bug that we should make a presubmit that checks the two are
the same?

[Steven Holte, 2014/11/04 02:44:20]

Done. https://code.google.com/p/chromium/issues/detail?id=429923

+-->
+
+<rappor-parameter-types>
+
+<rappor-parameters name="ETLD_PLUS_ONE">
+  <summary>
+    Parameters suitable for collecting the domain and registry of a URL from
+    UMA opt-in users.
+  </summary>
+  <parameters num-cohorts="128"
+              bytes="16"
+              hash-functions="2"
+              fake-prob=".5"
+              fake-one-prob=".5"
+              one-coin-prob=".75"
+              zero-coin-prob=".25"
+              always-enabled="false">
+  </parameters>
+</rappor-parameters>
+
+<rappor-parameters name="FULL_POPULATION">
+  <summary>
+    Parameters suitable for metrics collected from the full population of
+    chrome users.

[Alexei Svitkine (slow), 2014/11/03 21:48:21]

Nit: capitalize Chrome

[Steven Holte, 2014/11/04 02:44:20]

Changed this description.

+  </summary>
+  <parameters num-cohorts="128"
+              bytes="1"
+              hash-functions="2"
+              fake-prob=".5"
+              fake-one-prob=".5"
+              one-coin-prob=".75"
+              zero-coin-prob=".25"
+              always-enabled="true">
+</rappor-parameters>
+
+</rappor-parameter-types>
+
 <!-- Rappor metric definitions -->
 
 <rappor-metrics>
 
 <rappor-metric name="Extensions.PossibleAdInjection2" type="ETLD_PLUS_ONE">
   <owner>rdevlin.cronin@chromium.org</owner>
   <summary>
     The eTLD+1 of a URL that might be doing ad injection.
   </summary>
 </rappor-metric>
@@ skipping 27 matching lines @@
   <owner>holte@chromium.org</owner>
   <summary>
     The domain and registry of the URL chrome://newtab is rewritten to.
     Recorded when a profile is loaded, if the URL is valid.
   </summary>
 </rappor-metric>
 
 </rappor-metrics>
 
 </rappor-configuration>