Add UMA stats for pen palette

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 fe96f227a9568b3257f681042ac72c97e71942a3..1e8f06ca4c9d6da71ae9f865496410d4fc28d299 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1512,6 +1512,43 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Ash.Shelf.Palette.InLaserPointerMode" units="ms">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Tracks the amount of time spend in Palette laser point mode.
+  </summary>
+</histogram>
+
+<histogram name="Ash.Shelf.Palette.InMagnifyMode" units="ms">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>Tracks the amount of time spend in Palette Magnify mode.</summary>
+</histogram>
+
+<histogram name="Ash.Shelf.Palette.ModeCancellation"
+    enum="PaletteModeCancelType">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Tracks the number of times a palette mode is explicitly cancelled or
+    switched out of.
+  </summary>
+</histogram>
+
+<histogram name="Ash.Shelf.Palette.Usage" enum="PaletteTrayOptions">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Tracks the usage of each pen palette option when palette is not
+    automatically opened by a stylus eject event.
+  </summary>
+</histogram>
+
+<histogram name="Ash.Shelf.Palette.Usage.AutoOpened" enum="PaletteTrayOptions">
+  <owner>xiaoyinh@chromium.org</owner>
+  <summary>
+    Tracks the usage of each pen palette option when palette is automatically
+    opened by a stylus eject event.
+  </summary>
+</histogram>
+
 <histogram name="Ash.Shelf.TimeBetweenNavigateToTaskSwitches" units="seconds">
   <owner>bruthig@google.com</owner>
   <owner>tdanderson@google.com</owner>
@@ -89496,6 +89533,24 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="8" label="Unknown"/>
 </enum>
 
+<enum name="PaletteModeCancelType" type="int">
+  <int value="0" label="Palette laser pointer mode is cancelled."/>
+  <int value="1" label="Palette laser pointer mode is switched out of"/>
+  <int value="2" label="Palette magnify mode is cancelled."/>
+  <int value="3" label="Palette magnify mode is switched out of."/>
+</enum>
+
+<enum name="PaletteTrayOptions" type="int">
+  <int value="0" label="Palette being closed or dismissed with no action"/>
+  <int value="1" label="Click on the settings button"/>
+  <int value="2" label="Click on the help button"/>
+  <int value="3" label="Capture region"/>
+  <int value="4" label="Capture screen"/>
+  <int value="5" label="Add new note"/>
+  <int value="6" label="Magnifying glass mode"/>
+  <int value="7" label="Laser pointer mode"/>
+</enum>
+
 <enum name="PanningModelType" type="int">
   <int value="0" label="equalpower"/>
   <int value="1" label="HRTF"/>