Don't dismiss Settings when another view controller is presented on top

ios/chrome/browser/ui/settings/settings_navigation_controller.mm

 // 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 "ios/chrome/browser/ui/settings/settings_navigation_controller.h"
 
 #include "base/ios/ios_util.h"
 #import "base/ios/weak_nsobject.h"
 #include "base/mac/foundation_util.h"
 #import "base/mac/scoped_nsobject.h"
@@ skipping 524 matching lines @@
       NOTREACHED()
           << "Unexpected command " << [sender tag]
           << " Settings commands must execute on the main browser state.";
   }
   [[self nextResponder] chromeExecuteCommand:sender];
 }
 
 #pragma mark - UIResponder
 
 - (NSArray*)keyCommands {
+  if ([self presentedViewController]) {
+    return nil;
+  }
   base::WeakNSObject<SettingsNavigationController> weakSelf(self);
   return @[
     [UIKeyCommand cr_keyCommandWithInput:UIKeyInputEscape
                            modifierFlags:Cr_UIKeyModifierNone
                                    title:nil
                                   action:^{
                                     [weakSelf closeSettings];
                                   }],
   ];
 }
@@ skipping 101 matching lines @@
   return [NSValue valueWithPointer:controller];
 }
 
 #pragma mark - UIResponder
 
 - (BOOL)canBecomeFirstResponder {
   return YES;
 }
 
 @end