Add an IPC method for Blink to call RapporService::RecordSample()

tools/metrics/rappor/rappor.xml

 <!--
 Copyright 2015 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.
 -->
 
 <rappor-configuration>
 <!--
 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
@@ skipping 338 matching lines @@
   </summary>
 </rappor-metric>
 
 <rappor-metric name="SoftwareReporter.FoundUwS" type="COARSE_RAPPOR_TYPE">
   <owner>mad@chromium.org</owner>
   <summary>
     The IDs of unwanted software found by the software reporter tool.
   </summary>
 </rappor-metric>
 
+<rappor-metric name="WebComponents.DocumentRegisterElement"

[Alexei Svitkine (slow), 2015/04/07 21:01:56]

This CL doesn't actually implement these, right?

If so probably better to have them in a separate CL that can be reviewed
together with the CL adding them.

[kojii, 2015/04/08 07:21:23]

Done, the CL is at https://codereview.chromium.org/1071463003/, and updated the
description.

+    type="ETLD_PLUS_ONE">
+  <owner>kojii@chromium.org</owner>
+  <summary>
+    The host of a URL that used Document::RegisterElement().
+  </summary>
+</rappor-metric>
+
+<rappor-metric name="WebComponents.ElementCreateShadowRoot"
+    type="ETLD_PLUS_ONE">
+  <owner>kojii@chromium.org</owner>
+  <summary>
+    The host of a URL that used Element::CreateShadowRoot().
+  </summary>
+</rappor-metric>
+
 <rappor-metric name="interstitial.harmful.domain" type="COARSE_RAPPOR_TYPE">
   <owner>nparker@chromium.org</owner>
   <summary>
     The domain+registry of a URL that triggered a safe-browsing UWS
     interstitial.
   </summary>
 </rappor-metric>
 
 <rappor-metric name="interstitial.malware.domain" type="COARSE_RAPPOR_TYPE">
   <owner>nparker@chromium.org</owner>
@@ skipping 15 matching lines @@
   <owner>nparker@chromium.org</owner>
   <summary>
     The domain+registry of a URL that triggered an SSL interstitial.     Domains
     for bad-clock warnings are not reported.
   </summary>
 </rappor-metric>
 
 </rappor-metrics>
 
 </rappor-configuration>