Implement MediaCaptureDevices.

content/browser/renderer_host/media/media_capture_devices_impl.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 "content/browser/renderer_host/media/media_capture_devices_impl.h"
+
+#include "content/browser/browser_main_loop.h"
+#include "content/browser/renderer_host/media/media_stream_manager.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+namespace {
+
+void EnsureMonitorCaptureDevices() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&MediaStreamManager::EnsureDeviceMonitorStarted,
+                 base::Unretained(
+                     BrowserMainLoop::GetInstance()->media_stream_manager())));
+}
+
+}  // namespace
+
+MediaCaptureDevices* MediaCaptureDevices::GetInstance() {
+  return MediaCaptureDevicesImpl::GetInstance();
+}
+
+MediaCaptureDevicesImpl* MediaCaptureDevicesImpl::GetInstance() {
+  return Singleton<MediaCaptureDevicesImpl>::get();
+}
+
+const MediaStreamDevices&
+MediaCaptureDevicesImpl::GetAudioCaptureDevices() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (!devices_enumerated_) {
+    EnsureMonitorCaptureDevices();
+    devices_enumerated_ = true;
+  }
+  return audio_devices_;
+}
+
+const MediaStreamDevices&
+MediaCaptureDevicesImpl::GetVideoCaptureDevices() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (!devices_enumerated_) {
+    EnsureMonitorCaptureDevices();
+    devices_enumerated_ = true;
+  }
+  return video_devices_;
+}
+
+void MediaCaptureDevicesImpl::OnAudioCaptureDevicesChanged(
+    const MediaStreamDevices& devices) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));

[wjia(left Chromium), 2014/03/07 04:32:43]

Do you really need this restriction? It seems this function and the video one
can be called on any thread.

[michaelbai, 2014/03/07 06:59:31]

Done.

+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&MediaCaptureDevicesImpl::UpdateAudioDevicesOnUIThread,
+                 base::Unretained(this), devices));
+}
+
+void MediaCaptureDevicesImpl::OnVideoCaptureDevicesChanged(
+    const MediaStreamDevices& devices) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&MediaCaptureDevicesImpl::UpdateVideoDevicesOnUIThread,
+                 base::Unretained(this), devices));
+}
+
+MediaCaptureDevicesImpl::MediaCaptureDevicesImpl()
+    : devices_enumerated_(false) {
+}
+
+MediaCaptureDevicesImpl::~MediaCaptureDevicesImpl() {
+}
+
+void MediaCaptureDevicesImpl::UpdateAudioDevicesOnUIThread(
+    const MediaStreamDevices& devices) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  devices_enumerated_ = true;
+  audio_devices_ = devices;
+}
+
+void MediaCaptureDevicesImpl::UpdateVideoDevicesOnUIThread(
+    const MediaStreamDevices& devices) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  devices_enumerated_ = true;
+  video_devices_ = devices;
+}
+
+}  // namespace content