Separate USB device permissions prompt logic into subclasses.

chrome/browser/ui/cocoa/extensions/device_permissions_view_controller.mm

 // Copyright 2014 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 "base/mac/bundle_locations.h"
 #include "base/strings/sys_string_conversions.h"
 #import "chrome/browser/ui/cocoa/extensions/device_permissions_dialog_controller.h"
 #import "chrome/browser/ui/cocoa/extensions/device_permissions_view_controller.h"
 #include "chrome/grit/generated_resources.h"
 #import "ui/base/l10n/l10n_util_mac.h"
@@ skipping 11 matching lines @@
     prompt_ = prompt;
   }
   return self;
 }
 
 - (IBAction)cancel:(id)sender {
   controller_->Dismissed();
 }
 
 - (IBAction)ok:(id)sender {
-  __block std::vector<scoped_refptr<device::UsbDevice>> devices;
   [[tableView_ selectedRowIndexes]
       enumerateIndexesUsingBlock:^(NSUInteger index, BOOL* stop) {
           prompt_->GrantDevicePermission(index);
       }];
   controller_->Dismissed();
 }
 
 - (void)devicesChanged {
   [tableView_ reloadData];
 }
@@ skipping 26 matching lines @@
     return base::SysUTF16ToNSString(prompt_->GetDeviceName(rowIndex));
   } else if (tableColumn == serialNumberColumn_) {
     return base::SysUTF16ToNSString(prompt_->GetDeviceSerialNumber(rowIndex));
   } else {
     NOTREACHED();
     return @"";
   }
 }
 
 @end