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 4400ab149aff1b051521b1e463b5e4a144f509e0..dc4d88a69a7e6ffb6953a0874a6c13fe2c990ab2 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -74494,6 +74494,24 @@ 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 stored/updated in an Indexed DB object store.

[Mark P, 2017/02/07 19:12:22]

Recorded upon any time an item is stored or updated, I assume?  (If yes, no
changes are necessary.)

Would it be useful to distinguish between "newly stored" and "updated"?

Also, if the key is an "array of keys", is each separate item (which you imply
are "sub keys") also emitted to?  (I assume the array value is always emitted
regardless.)

all the same questions apply below

[jsbell, 2017/02/07 19:54:57]

Yes. Made it "newly stored or updated"
Not really (but I stole your terminology). Also, it would be hard to implement
(for updates we can store without checking to see if a previous value exists.)
No - added further note to clarify. While I can imagine circumstances where that
would be useful (maybe no-one uses binary keys except inside arrays...)
gathering it now is not needed for anything - we're really just trying to
measure usage of (1) array keys to encourage Edge to implement, and (2) measure
uptake of binary keys when we finally ship that support.
Yes.

+  </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
+    stored/updated in an Indexed DB object store.
+  </summary>
+</histogram>
+
 <histogram name="WebCore.IndexedDB.OpenTime.Blocked" units="ms">
   <owner>cmumford@chromium.org</owner>
   <summary>
@@ -93700,6 +93718,15 @@ 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 of other keys.</int>

[Mark P, 2017/02/07 19:12:22]

nit: does "of other keys" add anything here?

[jsbell, 2017/02/07 19:54:56]

Not really. Dropped it.

+  <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