IndexedDB: Log exception messages

LayoutTests/storage/indexeddb/deleteIndex-expected.txt

Index: LayoutTests/storage/indexeddb/deleteIndex-expected.txt
diff --git a/LayoutTests/storage/indexeddb/deleteIndex-expected.txt b/LayoutTests/storage/indexeddb/deleteIndex-expected.txt
index 87a1db6cf6e2926e34179e2892a1e5ad255a5d85..6cba4cf94628dd1ad500bb902de7c45c36cc86bf 100644
--- a/LayoutTests/storage/indexeddb/deleteIndex-expected.txt
+++ b/LayoutTests/storage/indexeddb/deleteIndex-expected.txt
@@ -13,12 +13,14 @@ Expecting exception from objectStore.deleteIndex('first')
 PASS Exception was thrown.
 PASS code is DOMException.NOT_FOUND_ERR
 PASS ename is 'NotFoundError'
+Exception message: The specified index was not found.
 PASS objectStore.deleteIndex() threw exception TypeError: Not enough arguments.
 index = objectStore.createIndex('first', 'first');
 Expecting exception from objectStore.deleteIndex('FIRST')
 PASS Exception was thrown.
 PASS code is DOMException.NOT_FOUND_ERR
 PASS ename is 'NotFoundError'
+Exception message: The specified index was not found.
 index = objectStore.createIndex('second', 'second');
 returnValue = objectStore.deleteIndex('first');
 PASS returnValue is undefined
@@ -26,10 +28,12 @@ Expecting exception from db.createObjectStore('bar');
 PASS Exception was thrown.
 PASS code is DOMException.INVALID_STATE_ERR
 PASS ename is 'InvalidStateError'
+Exception message: The database is not running a version change transaction.
 Expecting exception from objectStore.deleteIndex('second')
 PASS Exception was thrown.
 PASS code is 0
 PASS ename is 'TransactionInactiveError'
+Exception message: The transaction has finished.
 PASS successfullyParsed is true
 
 TEST COMPLETE