chain: wrap saveNames() in a DB batch and use _saveNames() internally

lib/blockchain/chaindb.js

@@ -1917,6 +1917,25 @@ class ChainDB {
    */
 
   async saveNames(view, entry, revert) {
+    this.start();
+    try {
+      await this._saveNames(view, entry, revert);
+    } catch (e) {
+      this.drop();
+      throw e;
+    }
+    await this.commit();
+  }
+
+  /**
+   * Commit names to tree, assuming batch is started.
+   * @private
+   * @param {CoinView} view
+   * @param {ChainEntry} entry
+   * @param {Boolean} revert
+   */
+
+  async _saveNames(view, entry, revert) {
     for (const ns of view.names.values()) {
       const {nameHash} = ns;
 
@@ -1967,7 +1986,7 @@ class ChainDB {
     else
       this.put(layout.w.encode(entry.height), undo.encode());
 
-    return this.saveNames(view, entry, false);
+    return this._saveNames(view, entry, false);
   }
 
   /**
@@ -1992,7 +2011,7 @@ class ChainDB {
       this.del(layout.w.encode(entry.height));
     }
 
-    return this.saveNames(view, entry, true);
+    return this._saveNames(view, entry, true);
   }
 
   /**