Move device/usb classes from the FILE thread to UI thread.

chrome/browser/ui/views/extensions/device_permissions_dialog_view.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 "chrome/browser/ui/views/extensions/device_permissions_dialog_view.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/api/chrome_device_permissions_prompt.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/constrained_window/constrained_window_views.h"
@@ skipping 10 matching lines @@
 
 using device::UsbDevice;
 using extensions::DevicePermissionsPrompt;
 
 class DevicePermissionsTableModel
     : public ui::TableModel,
       public DevicePermissionsPrompt::Prompt::Observer {
  public:
   explicit DevicePermissionsTableModel(
       scoped_refptr<DevicePermissionsPrompt::Prompt> prompt)
-      : prompt_(prompt) {
+      : prompt_(prompt), observer_(nullptr) {
     prompt_->SetObserver(this);
   }
 
   ~DevicePermissionsTableModel() override { prompt_->SetObserver(nullptr); }
 
   // ui::TableModel
   int RowCount() override;
   base::string16 GetText(int row, int column) override;
   void SetObserver(ui::TableModelObserver* observer) override;
 
@@ skipping 113 matching lines @@
 
 gfx::Size DevicePermissionsDialogView::GetPreferredSize() const {
   return gfx::Size(500, 250);
 }
 
 void ChromeDevicePermissionsPrompt::ShowDialog() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   constrained_window::ShowWebModalDialogViews(
       new DevicePermissionsDialogView(delegate(), prompt()), web_contents());
 }