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 3b8cb6a73d0d2d37c9b945b40a745d5d9f21c57a..510cb1ebfad7a3d505bbb0a6b25e0f818e83409d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -36417,6 +36417,31 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </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="millisecond">
+  <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.FetchEventExecutionTime" units="millisecond">
   <owner>shimazu@chromium.org</owner>
   <summary>
@@ -36578,6 +36603,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </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>
@@ -63589,6 +63622,14 @@ 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_INITIALIZE"/>
+  <int value="3" label="MIGRATION_ERROR_FAILED"/>
+  <int value="4" label="MIGRATION_ERROR_DELETE_DISK_CACHE"/>
+</enum>
+
 <enum name="ServiceWorkerPlatformNotificationStatus" type="int">
   <int value="0" label="OK"/>
   <int value="1" label="Service Worker not found"/>