Separate USB device permissions prompt logic into subclasses.

extensions/browser/api/usb/usb_api.cc

 // 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.
 
 #include "extensions/browser/api/usb/usb_api.h"
 
 #include <string>
 #include <vector>
 
 #include "base/barrier_closure.h"
@@ skipping 623 matching lines @@
                           &filters[i]);
     }
   }
 
   prompt_ = ExtensionsAPIClient::Get()->CreateDevicePermissionsPrompt(
       GetAssociatedWebContents());
   if (!prompt_) {
     return RespondNow(Error(kErrorNotSupported));
   }
 
-  AddRef();
   prompt_->AskForUsbDevices(
-      this, extension(), browser_context(), multiple, filters);
+      extension(), browser_context(), multiple, filters,
+      base::Bind(&UsbGetUserSelectedDevicesFunction::OnDevicesChosen, this));
   return RespondLater();
 }
 
-void UsbGetUserSelectedDevicesFunction::OnUsbDevicesChosen(
+void UsbGetUserSelectedDevicesFunction::OnDevicesChosen(
     const std::vector<scoped_refptr<UsbDevice>>& devices) {
   scoped_ptr<base::ListValue> result(new base::ListValue());
   for (const auto& device : devices) {
     result->Append(PopulateDevice(device.get()));
   }
 
   Respond(OneArgument(result.release()));
-  Release();
 }
 
 UsbRequestAccessFunction::UsbRequestAccessFunction() {
 }
 
 UsbRequestAccessFunction::~UsbRequestAccessFunction() {
 }
 
 ExtensionFunction::ResponseAction UsbRequestAccessFunction::Run() {
   scoped_ptr<extensions::core_api::usb::RequestAccess::Params> parameters =
@@ skipping 514 matching lines @@
     ReleaseDeviceHandle(parameters_->handle);
 
     scoped_ptr<base::ListValue> error_args(new base::ListValue());
     error_args->AppendBoolean(false);
     // Returning arguments with an error is wrong but we're stuck with it.
     Respond(ErrorWithArguments(error_args.Pass(), kErrorResetDevice));
   }
 }
 
 }  // namespace extensions