Various page_load_metrics cleanups and improvements

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 2a918a2e7d7a98754f0e4d141e9f2a998b5e3aa3..aa9ba10ee0223b6237ecf7d98b130cb6244c4749 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -46617,6 +46617,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PageLoad.Internal.NavigationStartedInForeground"
+    enum="BooleanForeground">
+  <owner>bmcquade@chromium.org</owner>
+  <summary>Whether a navigation started in the foreground.</summary>
+</histogram>
+
 <histogram name="PageLoad.Internal.PageLoadCompleted.AfterAppBackground"
     enum="BooleanStartedCompleted">
   <owner>bmcquade@chromium.org</owner>
@@ -46633,6 +46639,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PageLoad.Internal.Prerender" enum="BooleanHit">
+  <owner>bmcquade@chromium.org</owner>
+  <summary>
+    Counts the number of prerender navigations. Only logs true values.
+  </summary>
+</histogram>
+
 <histogram name="PageLoad.Internal.ProvisionalAbortChainSize.ForwardBack"
     units="length">
   <owner>csharrison@chromium.org</owner>
@@ -84157,6 +84170,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Force Disabled"/>
 </enum>
 
+<enum name="BooleanForeground" type="int">
+  <int value="0" label="Background"/>
+  <int value="1" label="Foreground"/>
+</enum>
+
 <enum name="BooleanForegroundNotification" type="int">
   <int value="0" label="Background Notification"/>
   <int value="1" label="Foreground Notification"/>
@@ -99065,7 +99083,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <enum name="InternalErrorLoadEvent" type="int">
   <summary>Internal Errors in the page_load_metrics system</summary>
-  <int value="0" label="Invalid timing IPC sent from renderer"/>
+  <int value="0" label="Invalid timing IPC sent from renderer (deprecated)"/>
   <int value="1"
       label="IPC received while not tracking a relevant committed load"/>
   <int value="2" label="IPC received from a frame we navigated away from"/>
@@ -99081,6 +99099,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="9" label="No commit or failed provisional load received"/>
   <int value="10" label="No page load end time recorded"/>
   <int value="11" label="Timing IPC received from subframe"/>
+  <int value="12" label="Invalid timing IPC (invalid timing descendent)"/>
+  <int value="13" label="Invalid timing IPC (invalid behavior descendent)"/>
+  <int value="14" label="Invalid timing IPC (invalid timing)"/>
 </enum>
 
 <enum name="InterruptReason" type="int">