Prerender: Remove PerceivedPLT histograms

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 f070a42f80e21fa7a1b06a8ebe330b9510169707..091950b38b59d0d6fde697fa3b765a469233fdd1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -52095,6 +52095,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLT" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52106,6 +52109,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTFirstAfterMiss" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52118,6 +52124,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTFirstAfterMissAnyOnly" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52132,6 +52141,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTFirstAfterMissBoth" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52146,6 +52158,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTFirstAfterMissNonOverlapping" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52160,6 +52175,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Prerender.PerceivedPLTFirstAfterMissNonOverlappingOnly"
     units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52174,6 +52192,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTMatched" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52205,6 +52226,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTWindowed" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52217,6 +52241,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PerceivedPLTWindowNotMatched" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a user navigates to a page to when it loads. Since the pages
@@ -52302,6 +52329,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Prerender.PrerenderNotSwappedInPLT" units="ms">
+  <obsolete>
+    Deprecated 2017-03.
+  </obsolete>
   <owner>pasko@chromium.org</owner>
   <summary>
     For prerenders that finish loading before they are ever swapped in, their