ServiceWorker: Migrate the script cache backend from BlockFile to Simple

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 32eace5a1186eda83327a2d378cfcb13436c04fb..4af12a1b43e22836e7bfb78812c7b39b65712274 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -37010,6 +37010,31 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ServiceWorker.DiskCacheMigrator.MigrationResult"
+    enum="ServiceWorkerStatusCode">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    Records result of ServiceWorkerDiskCache migration from BlockFile to Simple.
+  </summary>
+</histogram>
+
+<histogram name="ServiceWorker.DiskCacheMigrator.MigrationTime"
+    units="milliseconds">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    Execution time of ServiceWorkerDiskCache migration from BlockFile to Simple.
+  </summary>
+</histogram>
+
+<histogram name="ServiceWorker.DiskCacheMigrator.NumberOfMigratedResources"
+    units="count">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    The counts of resources migrated by ServiceWorkerDiskCacheMigrator. This
+    includes the main script and imported scripts.
+  </summary>
+</histogram>
+
 <histogram name="ServiceWorker.FetchEvent.Time" units="milliseconds">
   <owner>shimazu@chromium.org</owner>
   <summary>
@@ -37201,6 +37226,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ServiceWorker.Storage.DiskCacheMigrationResult"
+    enum="ServiceWorkerDiskCacheMigrationResult">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    Records result of diskcache migration operations in ServiceWorkerStorage.
+  </summary>
+</histogram>
+
 <histogram name="ServiceWorker.UnhandledEventRatio" units="percent">
   <owner>kinuko@chromium.org</owner>
   <summary>
@@ -64947,6 +64980,20 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="2" label="Failed to delete ServiceWorkerDiskCache"/>
 </enum>
 
+<enum name="ServiceWorkerDiskCacheMigrationResult" type="int">
+  <int value="0" label="MIGRATION_OK"/>
+  <int value="1" label="MIGRATION_NOT_NECESSARY"/>
+  <int value="2" label="MIGRATION_ERROR_FAILED"/>
+</enum>
+
+<enum name="ServiceWorkerPlatformNotificationStatus" type="int">
+  <int value="0" label="OK"/>
+  <int value="1" label="Service Worker not found"/>
+  <int value="2" label="Service Worker error"/>
+  <int value="3" label="event.waitUntil promise rejected"/>
+  <int value="4" label="Database error"/>
+</enum>
+
 <enum name="ServiceWorkerReadResponseResult" type="int">
   <int value="0" label="OK"/>
   <int value="1" label="Read headers error"/>