[Offline Pages] Add UMA to record final offline request status and loading failed error code.

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 a8bdb8205870da0f7d4a9223ad72db7cd04bdd89..4a6502d8fe47aebd2b35d78b6261ad54613a2d57 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -42614,6 +42614,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Result of servicing requests that may contain offline page.</summary>
 </histogram>
 
+<histogram name="OfflinePages.Background.BackgroundLoadingFailedCode"
+    enum="NetErrorCodes">
+  <owner>chili@chromium.org</owner>
+  <summary>The error codes that caused a page load failure.</summary>
+</histogram>
+
 <histogram name="OfflinePages.Background.CctApiDisableStatus"
     enum="OfflinePagesCctApiPrerenderAllowedStatus">
   <owner>petewil@chromium.org</owner>
@@ -42673,6 +42679,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="OfflinePages.Background.FinalSavePageResult"
+    enum="OfflinePagesBackgroundSavePageResult">
+  <owner>chili@chromium.org</owner>
+  <summary>
+    Status code of background offlining requests at the final step.
+  </summary>
+</histogram>
+
 <histogram name="OfflinePages.Background.ImmediateStart.AvailableRequestCount">
   <owner>dougarnett@chromium.org</owner>
   <summary>
@@ -102755,6 +102769,20 @@ from previous Chrome versions.
   <int value="14" label="Background scheduler canceled processing"/>
 </enum>
 
+<enum name="OfflinePagesBackgroundSavePageResult" type="int">
+<!-- Generated from components/offline_pages/core/background/request_notifier.h -->
+
+  <int value="0" label="Success"/>
+  <int value="1" label="Loading failure"/>
+  <int value="2" label="Loading canceled"/>
+  <int value="3" label="Foreground canceled"/>
+  <int value="4" label="Save failed"/>
+  <int value="5" label="Expired"/>
+  <int value="6" label="Retry count exceeded"/>
+  <int value="7" label="Start count exceeded"/>
+  <int value="8" label="Removed"/>
+</enum>
+
 <enum name="OfflinePagesCctApiPrerenderAllowedStatus" type="int">
   <int value="0" label="PrerenderAllowed"/>
   <int value="1" label="ThirdPartyCookiesDisabled"/>
@@ -119190,6 +119218,8 @@ from previous Chrome versions.
 </histogram_suffixes>
 
 <histogram_suffixes name="OfflinePagesNamespace" separator=".">
+  <affected-histogram
+      name="OfflinePages.Background.BackgroundLoadingFailedCode"/>
   <suffix name="bookmark" label="Offline bookmark cache"/>
   <suffix name="last_n" label="Offline recent pages"/>
   <suffix name="async_loading" label="Offline async loaded pages"/>
@@ -119198,6 +119228,7 @@ from previous Chrome versions.
   <suffix name="ntp_suggestions" label="Offline ntp suggestions"/>
   <affected-histogram
       name="OfflinePages.Background.EffectiveConnectionType.SavePageLater"/>
+  <affected-histogram name="OfflinePages.Background.FinalSavePageResult"/>
   <affected-histogram name="OfflinePages.Background.OfflinerRequestStatus"/>
   <affected-histogram name="OfflinePages.Background.TimeToCanceled"/>
   <affected-histogram name="OfflinePages.Background.TimeToSaved"/>