Callbacks: Prevent add() from unlocking with-memory lists

Fixes gh-3469
Closes gh-3470

src/callbacks.js

@@ -69,7 +69,7 @@ jQuery.Callbacks = function( options ) {
 		fire = function() {
 
 			// Enforce single-firing
-			locked = options.once;
+			locked = locked || options.once;
 
 			// Execute callbacks for all pending executions,
 			// respecting firingIndex overrides and runtime changes

test/unit/callbacks.js

@@ -366,3 +366,24 @@ QUnit.test( "jQuery.Callbacks() - disabled callback doesn't fire (gh-1790)", fun
 	cb.fire();
 	assert.ok( !fired, "Disabled callback function didn't fire" );
 } );
+
+QUnit.test( "jQuery.Callbacks() - list with memory stays locked (gh-3469)", function( assert ) {
+
+	assert.expect( 3 );
+
+	var cb = jQuery.Callbacks( "memory" ),
+		fired = 0,
+		count1 = function() { fired += 1; },
+		count2 = function() { fired += 10; };
+
+	cb.add( count1 );
+	cb.fire();
+	assert.equal( fired, 1, "Pre-lock() fire" );
+
+	cb.lock();
+	cb.add( count2 );
+	assert.equal( fired, 11, "Post-lock() add" );
+
+	cb.fire();
+	assert.equal( fired, 11, "Post-lock() fire ignored" );
+} );