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

components/offline_pages/core/background/request_coordinator_unittest.cc

Index: components/offline_pages/core/background/request_coordinator_unittest.cc
diff --git a/components/offline_pages/core/background/request_coordinator_unittest.cc b/components/offline_pages/core/background/request_coordinator_unittest.cc
index 0c5030cb5ba73773293469ccff6193d02613a3c2..bf36ebc9be534f4797cb5fca127402cce60d3cb1 100644
--- a/components/offline_pages/core/background/request_coordinator_unittest.cc
+++ b/components/offline_pages/core/background/request_coordinator_unittest.cc
@@ -670,6 +670,9 @@ TEST_F(RequestCoordinatorTest, OfflinerDoneRequestSucceeded) {
   // Check that the observer got the notification that we succeeded, and that
   // the request got removed from the queue.
   EXPECT_TRUE(observer().completed_called());
+  histograms().ExpectBucketCount(
+      "OfflinePages.Background.FinalSavePageResult.bookmark", 0 /* SUCCESS */,
+      1);
   EXPECT_EQ(RequestCoordinator::BackgroundSavePageResult::SUCCESS,
             observer().last_status());
 }
@@ -739,6 +742,9 @@ TEST_F(RequestCoordinatorTest, OfflinerDoneRequestFailed) {
   // subsequent notification that the request was removed) since we exceeded
   // retry count.
   EXPECT_TRUE(observer().completed_called());
+  histograms().ExpectBucketCount(
+      "OfflinePages.Background.FinalSavePageResult.bookmark",
+      6 /* RETRY_COUNT_EXCEEDED */, 1);
   EXPECT_EQ(RequestCoordinator::BackgroundSavePageResult::RETRY_COUNT_EXCEEDED,
             observer().last_status());
 }