[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 e7795dcb639727f77d1b108418a32ece98406f51..c1797ed5548db0019cb3c9c55ae14b4a661534ad 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -42862,6 +42862,12 @@ 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>
@@ -42921,6 +42927,14 @@ 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>
@@ -103351,6 +103365,20 @@ from previous Chrome versions.
   <int value="14" label="Background scheduler canceled processing"/>
 </enum>
 
+<enum name="OfflinePagesBackgroundSavePageResult" type="int">

[Pete Williamson, 2017/03/17 20:50:56]

Why add this, wasn't it already present, or was it just to make sure the values
match our expectations?

[chili, 2017/03/17 21:17:18]

I actually misread. This is the request_notifier::BackgroundSavePageResult. The
other is offliner::RequestStatus... 

+<!-- 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"/>
@@ -119759,6 +119787,8 @@ 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"/>
@@ -119767,6 +119797,7 @@ 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"/>