Explicitly tag the "cancel" button as being triggered by escape....

chrome/browser/js_modal_dialog_mac.mm

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/js_modal_dialog.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "app/l10n_util_mac.h"
 #include "app/message_box_flags.h"
@@ skipping 121 matching lines @@
   dialog_ = alert;
   NSTextField* field = nil;
   if (text_field) {
     field = [helper textField];
     [field setStringValue:base::SysWideToNSString(default_prompt_text_)];
   }
   [alert setDelegate:helper];
   [alert setInformativeText:base::SysWideToNSString(message_text_)];
   [alert setMessageText:base::SysWideToNSString(title_)];
   [alert addButtonWithTitle:default_button];
-  if (!one_button)
-    [alert addButtonWithTitle:other_button];
+  if (!one_button) {
+    NSButton* other = [alert addButtonWithTitle:other_button];
+    [other setKeyEquivalent:@"\e"];
+  }
   if (display_suppress_checkbox_) {
     [alert setShowsSuppressionButton:YES];
     NSString* suppression_title = l10n_util::GetNSStringWithFixup(
         IDS_JAVASCRIPT_MESSAGEBOX_SUPPRESS_OPTION);
     [[alert suppressionButton] setTitle:suppression_title];
   }
 
   [alert beginSheetModalForWindow:nil  // nil here makes it app-modal
                     modalDelegate:helper
                    didEndSelector:@selector(alertDidEnd:returnCode:contextInfo:)
@@ skipping 24 matching lines @@
   NOTIMPLEMENTED();
   return nil;
 }
 
 void JavaScriptAppModalDialog::CloseModalDialog() {
   NSAlert* alert = dialog_;
   DCHECK([alert isKindOfClass:[NSAlert class]]);
   [NSApp endSheet:[alert window]];
   dialog_ = nil;
 }