Linux native notifications: Add server capabilities metrics

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 3d5b6881c4e57919cc042191a56c2e2e8753d1f4..6016f2e0423c547581d8cd5bae120c7a43990efd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -43801,6 +43801,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="Notifications.Freedesktop.Capabilities"
+    enum="BooleanSupported">

[Mark P, 2017/05/04 18:27:00]

When you changed the enum from
BooleanNotificationServerCapabilitySupported
to
BooleanSupported,
I notice you didn't change the code.

Yet, the first enum had supports = 0, not supported = 1, and BooleanSupported
does the opposite.

Can you confirm the current code and enum value is correct, i.e., the older
version was wrong?

This also remind me, have you tested this code using about:histograms?

[Tom (Use chromium acct), 2017/05/04 18:41:27]

It was wrong before, and is correct now.
Didn't know about that page, just tested/verified the histograms now!

+<!-- Name completed by histogram_suffixes name="FreedesktopNotificationCapabilitiesId" -->
+
+  <owner>thomasanderson@chromium.org</owner>
+  <summary>
+    Whether the notification server supports the capability in question.  (Linux
+    only) Logged when the proxy to /org/Freedesktop/Notifications is set up
+    successfully, which happens at most once on startup.
+  </summary>
+</histogram>
+
 <histogram name="Notifications.Icon.FileSize" units="bytes">
   <obsolete>
     Deprecated Nov 2016 in favor of Notifications.LoadFileSize.*
@@ -43842,6 +43854,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Notifications.Linux.BridgeInitializationStatus"
+    enum="LinuxNotificationBridgeStatusCode">
+  <owner>thomasanderson@chromium.org</owner>
+  <summary>
+    The status code for initializing NotificationPlatformBridgeLinux.  Logged on

[Mark P, 2017/05/04 18:27:00]

Linux only, as the histogram name implies?

[Tom (Use chromium acct), 2017/05/04 18:41:27]

Done.

+    each start up.
+  </summary>
+</histogram>
+
 <histogram name="Notifications.LoadFailTime" units="ms">
 <!-- Name completed by histogram_suffixes name="NotificationImageTypes" -->
 
@@ -43935,6 +43956,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Notifications.UsingNativeNotificationCenter"
+    enum="BooleanNativeNotifications">
+  <owner>thomasanderson@chromium.org</owner>
+  <summary>
+    Indicates if Chrome is using system notifications or the Chrome notification
+    center.  Logged on each start up.
+  </summary>
+</histogram>
+
 <histogram name="Notifications.XPCConnectionEvent" enum="XPCConnectionEvent">
   <owner>miguelg@chromium.org</owner>
   <owner>rsesek@chromium.org</owner>
@@ -86077,6 +86107,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Missing data in disk cache"/>
 </enum>
 
+<enum name="BooleanNativeNotifications" type="int">
+  <int value="0" label="Using Chrome notifications"/>
+  <int value="1" label="Using native notifications"/>
+</enum>
+
 <enum name="BooleanNavPreloadFinishedFirst" type="int">
   <int value="0" label="Worker preparation finished first"/>
   <int value="1" label="Navigation preload response arrived first"/>
@@ -103502,6 +103537,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="20" label="2.29"/>
 </enum>
 
+<enum name="LinuxNotificationBridgeStatusCode" type="int">
+  <int value="0" label="success"/>
+  <int value="1" label="native notifications not supported"/>
+  <int value="2" label="missing required capabilities"/>
+  <int value="3" label="could not connect to signals"/>
+</enum>
+
 <enum name="LinuxSandboxStatus" type="int">
   <int value="0" label="none"/>
   <int value="1" label="suid"/>
@@ -122032,6 +122074,20 @@ from previous Chrome versions.
   <affected-histogram name="FirstUserAction.BackgroundTime.MainIntent"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="FreedesktopNotificationCapabilitiesId" separator=".">
+  <suffix name="ActionIcons" label="action-icons capability"/>
+  <suffix name="Actions" label="actions capability"/>
+  <suffix name="Body" label="body capability"/>
+  <suffix name="BodyHyperlinks" label="body-hyperlinks capability"/>
+  <suffix name="BodyImages" label="body-images capability"/>
+  <suffix name="BodyMarkup" label="body-markup capability"/>
+  <suffix name="IconMulti" label="icon-multi capability"/>
+  <suffix name="IconStatic" label="icon-static capability"/>
+  <suffix name="Persistence" label="persistence capability"/>
+  <suffix name="Sound" label="sound capability"/>
+  <affected-histogram name="Notifications.Freedesktop.Capabilities"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="FromGWS">
   <suffix name="FromGWS"
       label="Only page loads that are a result of a navigation from a web