Implement the BackgroundFetch{Fail,ed} Service Worker events

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 643d0c92e04aa9eb2791e25a5b5be97f49f04857..2cafc6e350f72152881d7f97abdf5cbb1efd6f7b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -62915,6 +62915,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ServiceWorker.BackgroundFetchedEvent.Time" units="ms">
+  <owner>peter@chromium.org</owner>
+  <summary>
+    The time taken between dispatching a BackgroundFetchedEvent to a Service
+    Worker and receiving a message that it finished handling the event. Includes
+    the time for the waitUntil() promise to settle.
+  </summary>
+</histogram>
+
+<histogram name="ServiceWorker.BackgroundFetchFailEvent.Time" units="ms">
+  <owner>peter@chromium.org</owner>
+  <summary>
+    The time taken between dispatching a BackgroundFetchFailEvent to a Service
+    Worker and receiving a message that it finished handling the event. Includes
+    the time for the waitUntil() promise to settle.
+  </summary>
+</histogram>
+
 <histogram name="ServiceWorker.BackgroundSyncEvent.Time" units="ms">
   <owner>jkarlin@chromium.org</owner>
   <summary>
@@ -109401,6 +109419,8 @@ from previous Chrome versions.
   <int value="22" label="PAYMENT_REQUEST"/>
   <int value="23" label="BACKGROUND_FETCH_ABORT"/>
   <int value="24" label="BACKGROUND_FETCH_CLICK"/>
+  <int value="25" label="BACKGROUND_FETCH_FAIL"/>
+  <int value="26" label="BACKGROUND_FETCHED"/>
 </enum>
 
 <enum name="ServiceWorkerPreparationType" type="int">
@@ -115402,6 +115422,8 @@ from previous Chrome versions.
 <histogram_suffixes name="BackgroundFetchEvents" separator=".">
   <suffix name="AbortEvent" label="BackgroundFetchAbortEvent"/>
   <suffix name="ClickEvent" label="BackgroundFetchClickEvent"/>
+  <suffix name="FailEvent" label="BackgroundFetchFailEvent"/>
+  <suffix name="FetchedEvent" label="BackgroundFetchedEvent"/>
   <affected-histogram name="BackgroundFetch.EventDispatchFailure.Dispatch"/>
   <affected-histogram name="BackgroundFetch.EventDispatchFailure.FindWorker"/>
   <affected-histogram name="BackgroundFetch.EventDispatchFailure.StartWorker"/>