Redirect handling in resource prefetch predictor

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 aa083e83b395db11a79197c856ce191ae347b272..c08e5f2053b836c3af4bf5c2f61f341fd3173e4d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -49030,6 +49030,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ResourcePrefetchPredictor.HostRedirectTableRowCount">
+  <owner>alexilin@chromium.org</owner>
+  <summary>
+    The count of number of rows in the HostRedirectTable. This is effecively the
+    number of (host, final redirect) pairs in the database. This is measured at
+    startup and used to get an estimate of the data size.
+  </summary>
+</histogram>
+
 <histogram name="ResourcePrefetchPredictor.HostTableHostCount">
   <owner>zhenw@chromium.org</owner>
   <summary>
@@ -49415,6 +49424,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ResourcePrefetchPredictor.UrlRedirectTableRowCount">
+  <owner>alexilin@chromium.org</owner>
+  <summary>
+    The count of number of rows in the UrlRedirectTable. This is effectively the
+    number of (main frame URL, final redirect) pairs in the database. This is
+    measured at startup and used to get an estimate of the data size.
+  </summary>
+</histogram>
+
 <histogram name="ResourcePrefetchPredictor.UrlTableMainFrameUrlCount">
   <obsolete>
     Deprecated September 2016. No longer recorded.