Removing unused DRP 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 2e4e1b665d4b5cc6129874780de76fa107e3cec1..3773aa1760729d3108c258119f2a65bb02dfc6f5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -41433,65 +41433,88 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="PLT.NT_Connect" units="ms">
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from connectStart to connectEnd based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeConnect" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from domanLookupEnd to connectStart based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeDomainLookup" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from fetchStart to domainLookupStart based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeDomLoading" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016. Replaced by
+    PageLoad.DocumentTiming.NavigationToDOMContentLoadedEventFired.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from responseStart to domLoading based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeFetch" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from navigationStart to fetchStart based on Navigation Timing when no
     redirect.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeFetchRedirect" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from navigationStart to fetchStart excluding time spent on redirects
     based on Navigation Timing. Only page loads with redirects are considered.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeLoadEvent" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016. Replaced by
+    PageLoad.DocumentTiming.NavigationToLoadEventFired.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from domContentLoadedEventEnd to loadEventStart based on Navigation
     Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DelayBeforeRequest" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from connectEnd to requestStart based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_DomainLookup" units="ms">
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from domainLookupStart to domainLookupEnd based on Navigation Timing.
@@ -41522,35 +41545,45 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="PLT.NT_LoadEvent" units="ms">
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from loadEventStart to loadEventEnd based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_Redirect" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from redirectStart to redirectEnd based on Navigation Timing when
     redirects exist.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_Request" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016. Replaced by
+    PageLoad.ParseTiming.NavigationToParseStart.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from requestStart to responseStart based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.NT_Response" units="ms">
+  <obsolete>
+    Deprecated as of 7/19/2016. Replaced by PageLoad.ParseTiming.ParseDuration.
+  </obsolete>
   <owner>bolian@chromium.org</owner>
   <summary>
     Time from responseStart to responseEnd based on Navigation Timing.
   </summary>
 </histogram>
 
 <histogram name="PLT.PageUsed_PrerenderLoad" enum="PageUsed">
   <obsolete>
     Deprecated as of 5/02/2011.
   </obsolete>