ServiceWorker: Add UMA for ServiceWorkerDatabase

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 4cf9e40d5f5ffb77db96b5750a9b4c60da855d45..281c921b40fe1f3bc26567fa01bce41245f7d15e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -24356,6 +24356,28 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="ServiceWorker.Database.OpenResult"
+    enum="ServiceWorkerDatabaseStatus">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    Records result of opening a database for ServiceWorkerDatabase.
+  </summary>
+</histogram>
+
+<histogram name="ServiceWorker.Database.ReadResult"
+    enum="ServiceWorkerDatabaseStatus">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>Records result of read operations in ServiceWorkerDatabase.</summary>
+</histogram>
+
+<histogram name="ServiceWorker.Database.WriteResult"
+    enum="ServiceWorkerDatabaseStatus">
+  <owner>nhiroki@chromium.org</owner>
+  <summary>
+    Records result of write operations in ServiceWorkerDatabase.
+  </summary>
+</histogram>
+
 <histogram name="Settings.DefaultSearchProvider" enum="OmniboxSearchEngine">
   <obsolete>
     Deprecated in Chrome 30.  Use Search.DefaultSearchProviderType instead.
@@ -42620,6 +42642,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="10" label="SERVICE_UTILITY_SEMANTIC_CAPS_FAILED"/>
 </enum>
 
+<enum name="ServiceWorkerDatabaseStatus" type="int">
+  <int value="0" label="OK"/>
+  <int value="1" label="Not Found Error"/>
+  <int value="2" label="IO Error"/>
+  <int value="3" label="Corruption Error"/>
+  <int value="4" label="Operation Error"/>
+</enum>
+
 <enum name="SessionStartupPref" type="int">
   <int value="0" label="Open home page (unused)"/>
   <int value="1" label="Continue from last opened pages"/>