Add detailed histograms for navigator.share.

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 edfe252772965e0350e02f6d75f453a54ef84ed6..a51bd0bda294955bf74a30c1f554a71127419aaa 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -68836,6 +68836,28 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time for capturing one frame in window capturing.</summary>
 </histogram>
 
+<histogram name="WebShare.ApiCount" enum="WebShareMethod">
+  <owner>mgiuca@chromium.org</owner>
+  <summary>
+    Counts the number of calls to navigator.share. Includes both successful and
+    failed shares.
+  </summary>
+</histogram>
+
+<histogram name="WebShare.ShareOutcome" enum="WebShareOutcome">
+  <owner>mgiuca@chromium.org</owner>
+  <summary>
+    Records the outcome of calls to navigator.share. This will not count any
+    calls that never complete (e.g., if the page closes while the picker is
+    open). Therefore, DO NOT look at the raw percentages of this histogram;
+    instead, compare these numbers with the WebShare.ApiCount.Share total.
+
+    NOTE: At the moment, if the user cancels the picker, its recording will be
+    delayed, and possibly never recorded (https://crbug.com/636274), so that
+    will account for a discrepancy between ShareOutcome and ApiCount.Share.
+  </summary>
+</histogram>
+
 <histogram name="WebsiteSettings.Action" enum="WebsiteSettingsAction">
   <owner>lgarron@chromium.org</owner>
   <summary>
@@ -98720,6 +98742,16 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="3" label="H264"/>
 </enum>
 
+<enum name="WebShareMethod" type="int">
+  <int value="0" label="Share"/>
+</enum>
+
+<enum name="WebShareOutcome" type="int">
+  <int value="0" label="Success"/>
+  <int value="1" label="UnknownFailure"/>
+  <int value="2" label="Canceled"/>
+</enum>
+
 <enum name="WebsiteSettingsAction" type="int">
   <int value="0" label="Opened"/>
   <int value="1" label="Selected Permissions tab"/>