Remove the backspace/shift+backspace navigating the page.

chrome/browser/global_keyboard_shortcuts_mac.mm

 // Copyright (c) 2011 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/global_keyboard_shortcuts_mac.h"
 
 #import <AppKit/AppKit.h>
 
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 85 matching lines @@
   return keyboard_shortcuts;
 }
 
 const KeyboardShortcutData* GetBrowserKeyboardShortcutTable(
     size_t* num_entries) {
   static const KeyboardShortcutData keyboard_shortcuts[] = {
     //cmd   shift  cntrl  option
     //---   -----  -----  ------
     {true,  false, false, false, kVK_LeftArrow,    0,   IDC_BACK},
     {true,  false, false, false, kVK_RightArrow,   0,   IDC_FORWARD},
-    {false, false, false, false, kVK_Delete,       0,   IDC_BACK},
-    {false, true,  false, false, kVK_Delete,       0,   IDC_FORWARD},
     {true,  true,  false, false, 0,                'c', IDC_DEV_TOOLS_INSPECT},
   };
 
   *num_entries = arraysize(keyboard_shortcuts);
 
   return keyboard_shortcuts;
 }
 
 static bool MatchesEventForKeyboardShortcut(
     const KeyboardShortcutData& shortcut,
@@ skipping 172 matching lines @@
       }
     }
 
     // opt/alt modifier is set (e.g. on german layout we want '{' for opt-8).
     if ([event modifierFlags] & NSAlternateKeyMask)
       return rawChar;
   }
 
   return noModifiersChar;
 }