Port messages sent by WebIDBCursorImpl to Mojo.

content/common/indexed_db/indexed_db.mojom

Index: content/common/indexed_db/indexed_db.mojom
diff --git a/content/common/indexed_db/indexed_db.mojom b/content/common/indexed_db/indexed_db.mojom
index ad69a5abd7567711dd6b1f91a0c4ac14462be5a3..39a47b85f0e1e1377a30938ec0ff566eabbf5cb6 100644
--- a/content/common/indexed_db/indexed_db.mojom
+++ b/content/common/indexed_db/indexed_db.mojom
@@ -111,11 +111,22 @@ interface Callbacks {
   SuccessDatabase(associated Database? database, DatabaseMetadata metadata);
 
   // Database::OpenCursor
-  SuccessCursor(int32 cursor_id, Key key, Key primary_key, Value? value);
+  SuccessCursor(associated Cursor cursor,
+                Key key,
+                Key primary_key,
+                Value? value);
 
   // Database::Get / Cursor::Advance
   SuccessValue(ReturnValue? value);
 
+  // Cursor::Continue / Advance
+  SuccessCursorContinue(Key key, Key primary_key, Value? value);
+
+  // Cursor::Prefetch
+  SuccessCursorPrefetch(array<Key> keys,
+                        array<Key> primary_keys,
+                        array<Value> values);
+
   // Database::GetAll
   SuccessArray(array<ReturnValue> values);
 
@@ -141,6 +152,14 @@ interface DatabaseCallbacks {
   Complete(int64 transaction_id);
 };
 
+interface Cursor {
+  Advance(uint32 count, associated Callbacks callbacks);
+  Continue(Key key, Key primary_key, associated Callbacks callbacks);
+  Prefetch(int32 count, associated Callbacks callbacks);
+  PrefetchReset(int32 used_prefetches, int32 unused_prefetches,
+                array<string> unused_blob_uuids);
+};
+
 interface Database {
   CreateObjectStore(int64 transaction_id,
                     int64 object_store_id,