RenderWidget popup should be a NSWindow so it can go outside the main window.

content/public/browser/event_hook_application_mac.mm

+// Copyright (c) 2012 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 "content/public/browser/event_hook_application_mac.h"
+
+#import "base/mac/scoped_sending_event.h"
+#import "base/logging.h"
+
+@implementation EventHookApplication
+
+// Initialize NSApplication using the custom subclass.  Check whether NSApp
+// was already initialized using another class, because that would break
+// some things.
++ (NSApplication*)sharedApplication {
+  NSApplication* app = [super sharedApplication];
+
+  // +sharedApplication initializes the global NSApp, so if a specific
+  // NSApplication subclass is requested, require that to be the one
+  // delivered.  The practical effect is to require a consistent NSApp
+  // across the executable.
+  CHECK([NSApp isKindOfClass:self])
+      << "NSApp must be of type " << [[self className] UTF8String]
+      << ", not " << [[NSApp className] UTF8String];
+
+  return app;
+}
+
+- (id)init {
+  if ((self = [super init])) {
+    eventHooks_.reset([[NSMutableArray alloc] init]);
+  }
+  return self;
+}
+
+- (void)addEventHook:(id<EventHookProtocol>)handler {
+  [eventHooks_ addObject:handler];
+}
+
+- (void)removeEventHook:(id<EventHookProtocol>)handler {
+  [eventHooks_ removeObject:handler];
+}
+
+- (void)sendEvent:(NSEvent*)event {
+  base::mac::ScopedSendingEvent sendingEventScoper;
+  for (id<EventHookProtocol> handler in eventHooks_.get()) {
+    [handler hookForEvent:event];
+  }
+  [super sendEvent:event];
+}
+
+@end