Giving focus to an app shim brings windows belonging to that app to the foreground.

ui/base/cocoa/focus_window_set.mm

Index: ui/base/cocoa/focus_window_set.mm
diff --git a/ui/base/cocoa/focus_window_set.mm b/ui/base/cocoa/focus_window_set.mm
new file mode 100644
index 0000000000000000000000000000000000000000..0505f053620afad1e0c74672eda17cc9736a4d91
--- /dev/null
+++ b/ui/base/cocoa/focus_window_set.mm
@@ -0,0 +1,26 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Cocoa/Cocoa.h>
+
+#include "ui/base/cocoa/focus_window_set.h"
+
+namespace ui {
+
+void FocusWindowSet(std::set<NSWindow*> windows) {
+  NSArray* ordered_windows = [NSApp orderedWindows];
+  [NSApp activateIgnoringOtherApps:YES];
+  NSWindow* last_window = nil;

[Nico, 2013/03/18 22:50:59]

Call this frontmost_window maybe

[jeremya, 2013/03/18 23:17:14]

Done.

+  for (int i = [ordered_windows count] - 1; i >= 0; i--) {
+    NSWindow* win = [ordered_windows objectAtIndex:i];
+    if (windows.find(win) != windows.end()) {
+      [win orderFront:nil];
+      last_window = win;
+    }
+  }
+  [last_window makeMainWindow];
+  [last_window makeKeyWindow];
+}
+
+}  // namespace ui