Extracting more than one wallpaper prominent color

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 78a757d7251b25850c11d988425f1852ccb3ed1e..03585674bf0ed2a80180c2a70038a1c717fedf3b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -2529,7 +2529,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>tbuckley@chromium.org</owner>
   <summary>
     The time taken to extract colors from wallpapers. Recorded each time the
-    wallpaper image changes.
+    wallpaper image changes. It may contain multiple colors extracted.
   </summary>
 </histogram>
 
@@ -2540,11 +2540,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
     The time taken to extract colors from 'expensive' wallpapers. Recorded each
     time the wallpaper image changes and the color extraction is expected to be
     expensive, e.g. image size &gt; 100 pixels. This includes time spent
-    switching threads.
+    switching threads. It may contain multiple colors extracted.
   </summary>
 </histogram>
 
 <histogram name="Ash.Wallpaper.ColorExtractionResult" enum="BooleanSuccess">
+  <obsolete>
+    Deprecated as of 6/2017.
+  </obsolete>
   <owner>bruthig@chromium.org</owner>
   <owner>tbuckley@chromium.org</owner>
   <summary>
@@ -2553,6 +2556,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Ash.Wallpaper.ColorExtractionResultEnum"

[Ilya Sherman, 2017/06/21 17:07:51]

Optional nit: I'd name this ColorExtractionResult2 instead of "Enum", but up to
you and the other metric owners.

[Qiang(Joe) Xu, 2017/06/21 22:35:27]

Done.

+    enum="WallpaperColorExtractionResult">
+  <owner>warx@chromium.org</owner>
+  <owner>tbuckley@chromium.org</owner>
+  <summary>
+    Tracks the success rate for wallpaper color extraction. Recorded each time
+    time the wallpaper image changes for each extracted wallpaper prominent
+    color.

[Ilya Sherman, 2017/06/21 17:07:51]

Is this description still correct?  It doesn't seem like the enum values measure
success; at least, if they do, it's not clear what values are success vs.
failure.

[Qiang(Joe) Xu, 2017/06/21 22:35:27]

I think it is still correct. I changed the label description in enums.xml for
representing success vs failure.

+  </summary>
+</histogram>
+
 <histogram name="Ash.Wallpaper.CustomLayout" enum="WallpaperLayout">
   <owner>xdai@chromium.org</owner>
   <summary>