Turns out nobody filed bugs for all these error names. And since IDL …

…is not being maintained...

Overview.src.html

@@ -635,6 +635,42 @@ <h3>Error names</h3>
   <td>"<dfn><code>NotReadableError</code></dfn>"
   <td>The I/O read operation failed.
   <td>&mdash;
+ <tr>
+  <!-- Indexed DB / Web Crypto -->
+  <td>"<dfn><code>UnknownError</code></dfn>"
+  <td>The operation failed for an unknown transient reason (e.g. out of memory).
+  <!-- The operation failed for reasons unrelated to the database itself and not covered by any other errors. -->
+  <td>&mdash;
+ <tr>
+  <!-- Indexed DB -->
+  <td>"<dfn><code>ConstraintError</code></dfn>"
+  <td>A mutation operation in a transaction failed because a constraint was not satisfied.
+  <td>&mdash;
+ <tr>
+  <!-- Indexed DB / Web Crypto -->
+  <td>"<dfn><code>DataError</code></dfn>"
+  <td>Provided data is inadequate.
+  <td>&mdash;
+ <tr>
+  <!-- Indexed DB -->
+  <td>"<dfn><code>TransactionInactiveError</code></dfn>"
+  <td>A request was placed against a transaction which is currently not active, or which is finished.
+  <td>&mdash;
+ <tr>
+  <!-- Indexed DB -->
+  <td>"<dfn><code>ReadOnlyError</code></dfn>"
+  <td>The mutating operation was attempted in a "readonly" transaction.
+  <td>&mdash;
+ <tr>
+  <!-- Indexed DB -->
+  <td>"<dfn><code>VersionError</code></dfn>"
+  <td>An attempt was made to open a database using a lower version than the existing version.
+  <td>&mdash;
+ <tr>
+  <!-- Web Crypto -->
+  <td>"<dfn><code>OperationError</code></dfn>"
+  <td>The operation failed for an operation-specific reason.
+  <td>&mdash;
 </table>