Add the Windows.IsPinnedToTaskbar metric.

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 e352d6fe66651dde518cc2e79709920ebe98e461..9f64f770c603f5d9e7ff775feb4d7c2aa13372c7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -64120,6 +64120,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Windows.IsPinnedToTaskbar" enum="Boolean">
+  <owner>pmonette@chromium.org</owner>
+  <summary>
+    This boolean indicates whether Chrome is pinned to the Windows taskbar for

[gab, 2016/06/28 20:59:18]

s/This boolean indicates/Indicates/ (type is already declared above)

(same below)

[Patrick Monette, 2016/06/28 23:22:25]

Done.

+    the current user.
+  </summary>
+</histogram>
+
+<histogram name="Windows.IsPinnedToTaskbar.Succeeded" enum="BooleanSuccess">
+  <owner>pmonette@chromium.org</owner>
+  <summary>
+    This boolean indicates whether an error occured while checking if Chrome is
+    pinned to the Windows taskbar for the current user.
+  </summary>
+</histogram>
+
 <histogram name="Windows.Kernel32Version" enum="WindowsVersion">
   <owner>scottmg@chromium.org</owner>
   <summary>
@@ -64137,6 +64153,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Windows.ShellHandlerProcessError">
+  <owner>pmonette@chromium.org</owner>
+  <summary>
+    The count of connection errors that happened between the browser and the

[gab, 2016/06/28 20:59:18]

As mentioned above, this always reports, as such it's only a count on the
server-side, but this description aims to describe what it means for a given
user and as such BooleanHit is more appropriate.

[Patrick Monette, 2016/06/28 23:22:25]

Done.

+    shell handler process. This is usually caused by a crash in the utility
+    process.
+  </summary>
+</histogram>
+
 <histogram name="Windows.Tablet" enum="BooleanTablet">
   <owner>zturner@chromium.org</owner>
   <summary>Count of browser launches from a Windows tablet pc.</summary>