predictors: Add RedirectStatus histogram + fix redirects related bug.

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 102d9ce5b5d82f8afcb3baefefce271c0a7216d4..2657bcd3d75d0ca5db317e6c75609a00a05bfceb 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -55789,6 +55789,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ResourcePrefetchPredictor.RedirectStatus"
+    enum="ResourcePrefetchPredictorRedirectStatus">
+  <owner>alexilin@chromium.org</owner>
+  <summary>
+    When the prefetch predictor has resources in the local database for a given
+    navigation, records stats about whether redirect was predicted correctly or
+    incorrectly.
+  </summary>
+</histogram>
+
 <histogram name="ResourcePrefetchPredictor.ReportingEvent"
     enum="ResourcePrefetchPredictorReportingEvent">
   <owner>alexilin@chromium.org</owner>
@@ -105745,6 +105755,14 @@ value.
   <int value="7" label="CONNECTION_BLUETOOTH"/>
 </enum>
 
+<enum name="ResourcePrefetchPredictorRedirectStatus" type="int">
+  <int value="0" label="NO_REDIRECT"/>
+  <int value="1" label="NO_REDIRECT_BUT_PREDICTED"/>
+  <int value="2" label="REDIRECT_NOT_PREDICTED"/>
+  <int value="3" label="REDIRECT_WRONG_PREDICTED"/>
+  <int value="4" label="REDIRECT_CORRECTLY_PREDICTED"/>
+</enum>
+
 <enum name="ResourcePrefetchPredictorReportingEvent" type="int">
   <int value="0" label="REPORTING_EVENT_ALL_HISTORY_CLEARED"/>
   <int value="1" label="REPORTING_EVENT_PARTIAL_HISTORY_CLEARED"/>