Replace the ExtensionHost load UMAs (Extensions.BackgroundPageLoadTime and friends)

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 b736f7de677dd451846ee0a2d042034a871a62f9..9ed152e34e17cc77518dcac5e60d72d897dc9204 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -7963,10 +7963,21 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Extensions.BackgroundPageLoadTime" units="milliseconds">
+  <obsolete>
+    Replaced by Extensions.BackgroundPageLoadTime2.
+  </obsolete>
   <owner>kalman@chromium.org</owner>
   <summary>The time for an extension's background page to load.</summary>
 </histogram>
 
+<histogram name="Extensions.BackgroundPageLoadTime2" units="milliseconds">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    The time taken for an extension's persistent background page to load its
+    initial URL.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.BackgroundPageType"
     units="ExtensionBackgroundPageType">
   <owner>kalman@chromium.org</owner>
@@ -8070,6 +8081,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Extensions.DialogLoadTime" units="milliseconds">
+  <obsolete>
+    There is no such thing as an extension dialog.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The time for a dialog-hosted extension to load.</summary>
 </histogram>
@@ -8197,20 +8211,41 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Extensions.EventPageActiveTime" units="milliseconds">
+  <obsolete>
+    Replaced by Extensions.EventPageActiveTime2.
+  </obsolete>
   <owner>kalman@chromium.org</owner>
   <summary>The time an extension's event page has spent loaded.</summary>
 </histogram>
 
+<histogram name="Extensions.EventPageActiveTime2" units="milliseconds">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    The time between an extension's event page loading its first URL and the
+    event page later shutting down.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.EventPageIdleTime" units="milliseconds">
   <owner>kalman@chromium.org</owner>
   <summary>The time an extension's event page has spent unloaded.</summary>
 </histogram>
 
 <histogram name="Extensions.EventPageLoadTime" units="milliseconds">
+  <obsolete>
+    Replaced by Extensions.EventPageLoadTime2.
+  </obsolete>
   <owner>kalman@chromium.org</owner>
   <summary>The time for an extension's event page to load.</summary>
 </histogram>
 
+<histogram name="Extensions.EventPageLoadTime2" units="milliseconds">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    The time taken for an extension's event page to load its initial URL.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ExtensionCacheCount">
   <owner>dpolukhin@chromium.org</owner>
   <summary>
@@ -9008,6 +9043,23 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.PopupLoadTime" units="milliseconds">
+  <obsolete>
+    Replaced by Extensions.PopupLoadTime2.
+  </obsolete>
+  <owner>kalman@chromium.org</owner>
+  <summary>The time for an Extension's popup to load.</summary>
+</histogram>
+
+<histogram name="Extensions.PopupLoadTime2" units="milliseconds">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    The time taken for an extension popup to load its initial URL. This may not
+    include the time taken for an extension process to start, if the extension
+    already has a background page running.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ProcessManagerStartupHostsTime"
     units="milliseconds">
   <owner>yoz@chromium.org</owner>