Add new experimental IDBObjectStore.getKey(query) API

content/browser/indexed_db/indexed_db_database.cc

Index: content/browser/indexed_db/indexed_db_database.cc
diff --git a/content/browser/indexed_db/indexed_db_database.cc b/content/browser/indexed_db/indexed_db_database.cc
index 032d01d211d929294ba4454a006faa4616b62caa..8dcea537cb067ad66a50ba5d564e107d14bf8e9f 100644
--- a/content/browser/indexed_db/indexed_db_database.cc
+++ b/content/browser/indexed_db/indexed_db_database.cc
@@ -883,15 +883,16 @@ void IndexedDBDatabase::GetOperation(
     key = &key_range->lower();
   } else {
     if (index_id == IndexedDBIndexMetadata::kInvalidId) {
-      DCHECK_NE(cursor_type, indexed_db::CURSOR_KEY_ONLY);
       // ObjectStore Retrieval Operation
-      backing_store_cursor = backing_store_->OpenObjectStoreCursor(
-          transaction->BackingStoreTransaction(),
-          id(),
-          object_store_id,
-          *key_range,
-          blink::WebIDBCursorDirectionNext,
-          &s);
+      if (cursor_type == indexed_db::CURSOR_KEY_ONLY) {
+        backing_store_cursor = backing_store_->OpenObjectStoreKeyCursor(
+            transaction->BackingStoreTransaction(), id(), object_store_id,
+            *key_range, blink::WebIDBCursorDirectionNext, &s);
+      } else {
+        backing_store_cursor = backing_store_->OpenObjectStoreCursor(
+            transaction->BackingStoreTransaction(), id(), object_store_id,
+            *key_range, blink::WebIDBCursorDirectionNext, &s);
+      }
     } else if (cursor_type == indexed_db::CURSOR_KEY_ONLY) {
       // Index Value Retrieval Operation
       backing_store_cursor = backing_store_->OpenIndexKeyCursor(
@@ -955,6 +956,11 @@ void IndexedDBDatabase::GetOperation(
       return;
     }
 
+    if (cursor_type == indexed_db::CURSOR_KEY_ONLY) {
+      callbacks->OnSuccess(*key);
+      return;
+    }
+
     if (object_store_metadata.auto_increment &&
         !object_store_metadata.key_path.IsNull()) {
       value.primary_key = *key;