Move UsbService to its own component.

chrome/browser/usb/usb_context.cc

-// Copyright 2013 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/usb/usb_context.h"
-
-#include "base/logging.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/threading/platform_thread.h"
-#include "third_party/libusb/src/libusb/interrupt.h"
-#include "third_party/libusb/src/libusb/libusb.h"
-
-// The UsbEventHandler works around a design flaw in the libusb interface. There
-// is currently no way to signal to libusb that any caller into one of the event
-// handler calls should return without handling any events.
-class UsbContext::UsbEventHandler : public base::PlatformThread::Delegate {
- public:
-  explicit UsbEventHandler(libusb_context* context);
-  virtual ~UsbEventHandler();
-
-  // base::PlatformThread::Delegate
-  virtual void ThreadMain() OVERRIDE;
-
- private:
-  volatile bool running_;
-  libusb_context* context_;
-  base::PlatformThreadHandle thread_handle_;
-  base::WaitableEvent start_polling_;
-  DISALLOW_COPY_AND_ASSIGN(UsbEventHandler);
-};
-
-UsbContext::UsbEventHandler::UsbEventHandler(libusb_context* context)
-    : running_(true),
-      context_(context),
-      thread_handle_(0),
-      start_polling_(false, false) {
-  bool success = base::PlatformThread::Create(0, this, &thread_handle_);
-  DCHECK(success) << "Failed to create USB IO handling thread.";
-  start_polling_.Wait();
-}
-
-UsbContext::UsbEventHandler::~UsbEventHandler() {
-  running_ = false;
-  // Spreading running_ to the UsbEventHandler thread.
-  base::subtle::MemoryBarrier();
-  libusb_interrupt_handle_event(context_);
-  base::PlatformThread::Join(thread_handle_);
-}
-
-void UsbContext::UsbEventHandler::ThreadMain() {
-  base::PlatformThread::SetName("UsbEventHandler");
-  VLOG(1) << "UsbEventHandler started.";
-  if (running_) {
-    start_polling_.Signal();
-    libusb_handle_events(context_);
-  }
-  while (running_)
-    libusb_handle_events(context_);
-  VLOG(1) << "UsbEventHandler shutting down.";
-}
-
-UsbContext::UsbContext(PlatformUsbContext context) : context_(context) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  event_handler_ = new UsbEventHandler(context_);
-}
-
-UsbContext::~UsbContext() {
-  // destruction of UsbEventHandler is a blocking operation.
-  DCHECK(thread_checker_.CalledOnValidThread());
-  delete event_handler_;
-  event_handler_ = NULL;
-  libusb_exit(context_);
-}