IndexedDB: Add histograms for key type

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 616abde71e0a7d4efbecf5e45630c57ab9be3401..ba184dbd908ae93f6aa83b65f877ac073716a060 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -74671,6 +74671,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebCore.IndexedDB.ObjectStore.IndexEntry.KeyType"
+    enum="IDBKeyType">
+  <owner>jsbell@chromium.org</owner>
+  <summary>
+    The type of key (number, string, etc.) used for an index entry for a record
+    being newly stored or updated in an Indexed DB object store. For array keys,
+    the types of sub-keys are not recorded.
+  </summary>
+</histogram>
+
+<histogram name="WebCore.IndexedDB.ObjectStore.Record.KeyType"
+    enum="IDBKeyType">
+  <owner>jsbell@chromium.org</owner>
+  <summary>
+    The type of key (number, string, etc.) used for a record being newly stored
+    or updated in an Indexed DB object store. For array keys, the types of
+    sub-keys are not recorded.
+  </summary>
+</histogram>
+
 <histogram name="WebCore.IndexedDB.OpenTime.Blocked" units="ms">
   <owner>cmumford@chromium.org</owner>
   <summary>
@@ -93963,6 +93983,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Array">Key path is an array of strings.</int>
 </enum>
 
+<enum name="IDBKeyType" type="int">
+  <int value="0" label="Invalid">Invalid key.</int>
+  <int value="1" label="Array">Key is an array.</int>
+  <int value="2" label="Binary">Key is a binary buffer.</int>
+  <int value="3" label="String">Key is a string.</int>
+  <int value="4" label="Date">Key is a date.</int>
+  <int value="5" label="Number">Key is a number.</int>
+</enum>
+
 <enum name="IDBLevelDBBackingStoreInternalErrorType" type="int">
   <int value="0" label="IDBLevelDBBackingStoreReadError">
     IndexedDB encountered an error attempting to read or decode a value from the