Remove dead histograms and actions

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 660df62d1f43ecd49f3bddef693bb5d0a2480bea..1647327fb2ceb6f08b9c2aea52c23638fff53193 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -21814,6 +21814,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Memory.Plugin" units="KB">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>hajimehoshi@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>
   <owner>kouhei@chromium.org</owner>
@@ -21824,6 +21827,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Memory.PluginProcessCount">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>hajimehoshi@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>
   <owner>kouhei@chromium.org</owner>
@@ -22226,6 +22232,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Memory.Swap.Plugin" units="KB">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>hajimehoshi@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>
   <owner>kouhei@chromium.org</owner>
@@ -38411,6 +38420,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Plugin.NpapiRemovalInfobar.Removed.PluginGroup"
     enum="PluginGroup">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>wfh@chromium.org</owner>
   <summary>
     The plugin group of an NPAPI plugin that is no longer supported. Recorded
@@ -38421,6 +38433,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Plugin.NpapiRemovalInfobar.RemovedSoon.PluginGroup"
     enum="PluginGroup">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>wfh@chromium.org</owner>
   <summary>
     The plugin group of an NPAPI plugin that will be unsupported soon. Recorded
@@ -38430,6 +38445,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Plugin.NPAPIStatus" enum="NPAPIPluginStatus">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>wfh@chromium.org</owner>
   <summary>
     Records whether NPAPI plugins are supported by the platform, and if so,
@@ -38504,6 +38522,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Plugin.SyncMessageTime" units="ms">
+  <obsolete>
+    Deprecated due to NPAPI removal.
+  </obsolete>
   <owner>gab@chromium.org</owner>
   <summary>
     Roundtrip times for synchronous IPC calls from the renderer to NPAPI plugin