Implement MediaCaptureDevices.

- Added MediaCaptureDevices to cache the MediaCaptureDevice in content layer.
- Removed the correspoding methods in MediaObserver.
- Removed the MediaDevicesMonitor APIs.

BUG=348867
TBR=mnissler

Review URL: https://codereview.chromium.org/183743021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257198 0039d316-1c4b-4281-b951-d872f2087c98

12 files changed, 244 insertions, 111 deletions

diff --git a/chrome/browser/media/media_capture_devices_dispatcher.cc b/chrome/browser/media/media_capture_devices_dispatcher.cc
index 6030ab2..0da0a4c 100644
--- a/chrome/browser/media/media_capture_devices_dispatcher.cc
+++ b/chrome/browser/media/media_capture_devices_dispatcher.cc
@@ -25,7 +25,7 @@
 #include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/desktop_media_id.h"
-#include "content/public/browser/media_devices_monitor.h"
+#include "content/public/browser/media_capture_devices.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
@@ -51,6 +51,7 @@
 #endif  // !defined(OS_ANDROID) && !defined(OS_IOS)
 
 using content::BrowserThread;
+using content::MediaCaptureDevices;
 using content::MediaStreamDevices;
 
 namespace {
@@ -247,8 +248,7 @@ MediaCaptureDevicesDispatcher* MediaCaptureDevicesDispatcher::GetInstance() {
 }
 
 MediaCaptureDevicesDispatcher::MediaCaptureDevicesDispatcher()
-    : devices_enumerated_(false),
-      is_device_enumeration_disabled_(false),
+    : is_device_enumeration_disabled_(false),
       media_stream_capture_indicator_(new MediaStreamCaptureIndicator()) {
   // MediaCaptureDevicesDispatcher is a singleton. It should be created on
   // UI thread. Otherwise, it will not receive
@@ -288,21 +288,19 @@ void MediaCaptureDevicesDispatcher::RemoveObserver(Observer* observer) {
 const MediaStreamDevices&
 MediaCaptureDevicesDispatcher::GetAudioCaptureDevices() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (!is_device_enumeration_disabled_ && !devices_enumerated_) {
-    content::EnsureMonitorCaptureDevices();
-    devices_enumerated_ = true;
-  }
-  return audio_devices_;
+  if (is_device_enumeration_disabled_ || !test_audio_devices_.empty())
+    return test_audio_devices_;
+
+  return MediaCaptureDevices::GetInstance()->GetAudioCaptureDevices();
 }
 
 const MediaStreamDevices&
 MediaCaptureDevicesDispatcher::GetVideoCaptureDevices() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (!is_device_enumeration_disabled_ && !devices_enumerated_) {
-    content::EnsureMonitorCaptureDevices();
-    devices_enumerated_ = true;
-  }
-  return video_devices_;
+  if (is_device_enumeration_disabled_ || !test_video_devices_.empty())
+    return test_video_devices_;
+
+  return MediaCaptureDevices::GetInstance()->GetVideoCaptureDevices();
 }
 
 void MediaCaptureDevicesDispatcher::Observe(
@@ -743,22 +741,22 @@ MediaCaptureDevicesDispatcher::GetDesktopStreamsRegistry() {
   return desktop_streams_registry_.get();
 }
 
-void MediaCaptureDevicesDispatcher::OnAudioCaptureDevicesChanged(
-    const content::MediaStreamDevices& devices) {
+void MediaCaptureDevicesDispatcher::OnAudioCaptureDevicesChanged() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
-      base::Bind(&MediaCaptureDevicesDispatcher::UpdateAudioDevicesOnUIThread,
-                 base::Unretained(this), devices));
+      base::Bind(
+          &MediaCaptureDevicesDispatcher::NotifyAudioDevicesChangedOnUIThread,
+          base::Unretained(this)));
 }
 
-void MediaCaptureDevicesDispatcher::OnVideoCaptureDevicesChanged(
-    const content::MediaStreamDevices& devices) {
+void MediaCaptureDevicesDispatcher::OnVideoCaptureDevicesChanged() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
-      base::Bind(&MediaCaptureDevicesDispatcher::UpdateVideoDevicesOnUIThread,
-                 base::Unretained(this), devices));
+      base::Bind(
+          &MediaCaptureDevicesDispatcher::NotifyVideoDevicesChangedOnUIThread,
+          base::Unretained(this)));
 }
 
 void MediaCaptureDevicesDispatcher::OnMediaRequestStateChanged(
@@ -822,22 +820,16 @@ void MediaCaptureDevicesDispatcher::OnCreatingAudioStream(
           base::Unretained(this), render_process_id, render_frame_id));
 }
 
-void MediaCaptureDevicesDispatcher::UpdateAudioDevicesOnUIThread(
-    const content::MediaStreamDevices& devices) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  devices_enumerated_ = true;
-  audio_devices_ = devices;
+void MediaCaptureDevicesDispatcher::NotifyAudioDevicesChangedOnUIThread() {
+  MediaStreamDevices devices = GetAudioCaptureDevices();
   FOR_EACH_OBSERVER(Observer, observers_,
-                    OnUpdateAudioDevices(audio_devices_));
+                    OnUpdateAudioDevices(devices));
 }
 
-void MediaCaptureDevicesDispatcher::UpdateVideoDevicesOnUIThread(
-    const content::MediaStreamDevices& devices) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  devices_enumerated_ = true;
-  video_devices_ = devices;
+void MediaCaptureDevicesDispatcher::NotifyVideoDevicesChangedOnUIThread() {
+  MediaStreamDevices devices = GetVideoCaptureDevices();
   FOR_EACH_OBSERVER(Observer, observers_,
-                    OnUpdateVideoDevices(video_devices_));
+                    OnUpdateVideoDevices(devices));
 }
 
 void MediaCaptureDevicesDispatcher::UpdateMediaRequestStateOnUIThread(
@@ -931,3 +923,14 @@ bool MediaCaptureDevicesDispatcher::IsDesktopCaptureInProgress() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   return desktop_capture_sessions_.size() > 0;
 }
+
+
+void MediaCaptureDevicesDispatcher::SetTestAudioCaptureDevices(
+    const MediaStreamDevices& devices) {
+  test_audio_devices_ = devices;
+}
+
+void MediaCaptureDevicesDispatcher::SetTestVideoCaptureDevices(
+    const MediaStreamDevices& devices) {
+  test_video_devices_ = devices;
+}
diff --git a/chrome/browser/media/media_capture_devices_dispatcher.h b/chrome/browser/media/media_capture_devices_dispatcher.h
index 129c0ed1f..0c16f3b 100644
--- a/chrome/browser/media/media_capture_devices_dispatcher.h
+++ b/chrome/browser/media/media_capture_devices_dispatcher.h
@@ -112,10 +112,8 @@ class MediaCaptureDevicesDispatcher : public content::MediaObserver,
   void DisableDeviceEnumerationForTesting();
 
   // Overridden from content::MediaObserver:
-  virtual void OnAudioCaptureDevicesChanged(
-      const content::MediaStreamDevices& devices) OVERRIDE;
-  virtual void OnVideoCaptureDevicesChanged(
-      const content::MediaStreamDevices& devices) OVERRIDE;
+  virtual void OnAudioCaptureDevicesChanged() OVERRIDE;
+  virtual void OnVideoCaptureDevicesChanged() OVERRIDE;
   virtual void OnMediaRequestStateChanged(
       int render_process_id,
       int render_view_id,
@@ -141,6 +139,10 @@ class MediaCaptureDevicesDispatcher : public content::MediaObserver,
 
   bool IsDesktopCaptureInProgress();
 
+  // Only for testing.
+  void SetTestAudioCaptureDevices(const content::MediaStreamDevices& devices);
+  void SetTestVideoCaptureDevices(const content::MediaStreamDevices& devices);
+
  private:
   friend struct DefaultSingletonTraits<MediaCaptureDevicesDispatcher>;
 
@@ -197,8 +199,8 @@ class MediaCaptureDevicesDispatcher : public content::MediaObserver,
                                scoped_ptr<content::MediaStreamUI> ui);
 
   // Called by the MediaObserver() functions, executed on UI thread.
-  void UpdateAudioDevicesOnUIThread(const content::MediaStreamDevices& devices);
-  void UpdateVideoDevicesOnUIThread(const content::MediaStreamDevices& devices);
+  void NotifyAudioDevicesChangedOnUIThread();
+  void NotifyVideoDevicesChangedOnUIThread();
   void UpdateMediaRequestStateOnUIThread(
       int render_process_id,
       int render_view_id,
@@ -209,19 +211,15 @@ class MediaCaptureDevicesDispatcher : public content::MediaObserver,
   void OnCreatingAudioStreamOnUIThread(int render_process_id,
                                        int render_frame_id);
 
-  // A list of cached audio capture devices.
-  content::MediaStreamDevices audio_devices_;
+  // Only for testing, a list of cached audio capture devices.
+  content::MediaStreamDevices test_audio_devices_;
 
-  // A list of cached video capture devices.
-  content::MediaStreamDevices video_devices_;
+  // Only for testing, a list of cached video capture devices.
+  content::MediaStreamDevices test_video_devices_;
 
   // A list of observers for the device update notifications.
   ObserverList<Observer> observers_;
 
-  // Flag to indicate if device enumeration has been done/doing.
-  // Only accessed on UI thread.
-  bool devices_enumerated_;
-
   // Flag used by unittests to disable device enumeration.
   bool is_device_enumeration_disabled_;
 
diff --git a/chrome/browser/policy/policy_browsertest.cc b/chrome/browser/policy/policy_browsertest.cc
index 5271130..9c3ee31 100644
--- a/chrome/browser/policy/policy_browsertest.cc
+++ b/chrome/browser/policy/policy_browsertest.cc
@@ -2795,7 +2795,7 @@ IN_PROC_BROWSER_TEST_P(MediaStreamDevicesControllerBrowserTest,
 
   content::BrowserThread::PostTaskAndReply(
       content::BrowserThread::IO, FROM_HERE,
-      base::Bind(&MediaCaptureDevicesDispatcher::OnAudioCaptureDevicesChanged,
+      base::Bind(&MediaCaptureDevicesDispatcher::SetTestAudioCaptureDevices,
                  base::Unretained(MediaCaptureDevicesDispatcher::GetInstance()),
                  audio_devices),
       base::Bind(&MediaStreamDevicesControllerBrowserTest::FinishAudioTest,
@@ -2828,7 +2828,7 @@ IN_PROC_BROWSER_TEST_P(MediaStreamDevicesControllerBrowserTest,
     content::BrowserThread::PostTaskAndReply(
         content::BrowserThread::IO, FROM_HERE,
         base::Bind(
-            &MediaCaptureDevicesDispatcher::OnAudioCaptureDevicesChanged,
+            &MediaCaptureDevicesDispatcher::SetTestAudioCaptureDevices,
             base::Unretained(MediaCaptureDevicesDispatcher::GetInstance()),
             audio_devices),
         base::Bind(
@@ -2852,7 +2852,7 @@ IN_PROC_BROWSER_TEST_P(MediaStreamDevicesControllerBrowserTest,
 
   content::BrowserThread::PostTaskAndReply(
       content::BrowserThread::IO, FROM_HERE,
-      base::Bind(&MediaCaptureDevicesDispatcher::OnVideoCaptureDevicesChanged,
+      base::Bind(&MediaCaptureDevicesDispatcher::SetTestVideoCaptureDevices,
                  base::Unretained(MediaCaptureDevicesDispatcher::GetInstance()),
                  video_devices),
       base::Bind(&MediaStreamDevicesControllerBrowserTest::FinishVideoTest,
@@ -2884,8 +2884,7 @@ IN_PROC_BROWSER_TEST_P(MediaStreamDevicesControllerBrowserTest,
 
     content::BrowserThread::PostTaskAndReply(
         content::BrowserThread::IO, FROM_HERE,
-        base::Bind(
-            &MediaCaptureDevicesDispatcher::OnVideoCaptureDevicesChanged,
+        base::Bind(&MediaCaptureDevicesDispatcher::SetTestVideoCaptureDevices,
             base::Unretained(MediaCaptureDevicesDispatcher::GetInstance()),
             video_devices),
         base::Bind(
diff --git a/content/browser/media/media_devices_monitor.cc b/content/browser/media/media_devices_monitor.cc
deleted file mode 100644
index 9f2c183..0000000
--- a/content/browser/media/media_devices_monitor.cc
+++ /dev/null
@@ -1,28 +0,0 @@
-// 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 "content/public/browser/media_devices_monitor.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 EnsureMonitorCaptureDevicesInternal(
-    MediaStreamManager* media_stream_manager) {
-  media_stream_manager->EnsureDeviceMonitorStarted();
-}
-}
-
-void EnsureMonitorCaptureDevices() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&EnsureMonitorCaptureDevicesInternal,
-                 BrowserMainLoop::GetInstance()->media_stream_manager()));
-}
-
-}  // namespace content
diff --git a/content/browser/renderer_host/media/media_capture_devices_impl.cc b/content/browser/renderer_host/media/media_capture_devices_impl.cc
new file mode 100644
index 0000000..f4e13ab
--- /dev/null
+++ b/content/browser/renderer_host/media/media_capture_devices_impl.cc
@@ -0,0 +1,99 @@
+// 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) {
+  if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    UpdateAudioDevicesOnUIThread(devices);
+  } else {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&MediaCaptureDevicesImpl::UpdateAudioDevicesOnUIThread,
+                   base::Unretained(this), devices));
+  }
+}
+
+void MediaCaptureDevicesImpl::OnVideoCaptureDevicesChanged(
+    const MediaStreamDevices& devices) {
+  if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    UpdateVideoDevicesOnUIThread(devices);
+  } else {
+    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
diff --git a/content/browser/renderer_host/media/media_capture_devices_impl.h b/content/browser/renderer_host/media/media_capture_devices_impl.h
new file mode 100644
index 0000000..078f659
--- /dev/null
+++ b/content/browser/renderer_host/media/media_capture_devices_impl.h
@@ -0,0 +1,49 @@
+// 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.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H
+
+#include "base/memory/singleton.h"
+#include "content/public/browser/media_capture_devices.h"
+
+namespace content {
+
+class MediaCaptureDevicesImpl : public MediaCaptureDevices {
+ public:
+  static MediaCaptureDevicesImpl* GetInstance();
+
+  // Overriden from MediaCaptureDevices
+  virtual const MediaStreamDevices& GetAudioCaptureDevices() OVERRIDE;
+  virtual const MediaStreamDevices& GetVideoCaptureDevices() OVERRIDE;
+
+  // Called by MediaStreamManager to notify the change of media capture
+  // devices, these 2 methods are called in IO thread.
+  void OnAudioCaptureDevicesChanged(const MediaStreamDevices& devices);
+  void OnVideoCaptureDevicesChanged(const MediaStreamDevices& devices);
+
+ private:
+  friend struct DefaultSingletonTraits<MediaCaptureDevicesImpl>;
+  MediaCaptureDevicesImpl();
+  virtual ~MediaCaptureDevicesImpl();
+
+  void UpdateAudioDevicesOnUIThread(const content::MediaStreamDevices& devices);
+  void UpdateVideoDevicesOnUIThread(const content::MediaStreamDevices& devices);
+
+  // Flag to indicate if device enumeration has been done/doing.
+  // Only accessed on UI thread.
+  bool devices_enumerated_;
+
+  // A list of cached audio capture devices.
+  MediaStreamDevices audio_devices_;
+
+  // A list of cached video capture devices.
+  MediaStreamDevices video_devices_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaCaptureDevicesImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index e07c2da..c533891 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/content/browser/renderer_host/media/media_stream_manager.cc
@@ -19,6 +19,7 @@
 #include "content/browser/media/capture/web_contents_capture_util.h"
 #include "content/browser/renderer_host/media/audio_input_device_manager.h"
 #include "content/browser/renderer_host/media/device_request_message_filter.h"
+#include "content/browser/renderer_host/media/media_capture_devices_impl.h"
 #include "content/browser/renderer_host/media/media_stream_requester.h"
 #include "content/browser/renderer_host/media/media_stream_ui_proxy.h"
 #include "content/browser/renderer_host/media/video_capture_manager.h"
@@ -1791,9 +1792,13 @@ void MediaStreamManager::NotifyDevicesChanged(
   }
 
   if (IsAudioMediaType(stream_type)) {
-    media_observer->OnAudioCaptureDevicesChanged(new_devices);
+    MediaCaptureDevicesImpl::GetInstance()->OnAudioCaptureDevicesChanged(
+        new_devices);
+    media_observer->OnAudioCaptureDevicesChanged();
   } else if (IsVideoMediaType(stream_type)) {
-    media_observer->OnVideoCaptureDevicesChanged(new_devices);
+    MediaCaptureDevicesImpl::GetInstance()->OnVideoCaptureDevicesChanged(
+        new_devices);
+    media_observer->OnVideoCaptureDevicesChanged();
   } else {
     NOTREACHED();
   }
diff --git a/content/browser/renderer_host/media/mock_media_observer.h b/content/browser/renderer_host/media/mock_media_observer.h
index 24f0b24..04678c9 100644
--- a/content/browser/renderer_host/media/mock_media_observer.h
+++ b/content/browser/renderer_host/media/mock_media_observer.h
@@ -20,10 +20,6 @@ class MockMediaObserver : public MediaObserver {
   MockMediaObserver();
   virtual ~MockMediaObserver();
 
-  MOCK_METHOD1(OnAudioCaptureDevicesChanged,
-               void(const MediaStreamDevices& devices));
-  MOCK_METHOD1(OnVideoCaptureDevicesChanged,
-                 void(const MediaStreamDevices& devices));
   MOCK_METHOD6(OnMediaRequestStateChanged,
                void(int render_process_id, int render_view_id,
                     int page_request_id, const GURL& security_origin,
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index dacc1d4..4e943fc 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -129,9 +129,9 @@
     'public/browser/load_notification_details.h',
     'public/browser/local_storage_usage_info.cc',
     'public/browser/local_storage_usage_info.h',
+    'public/browser/media_capture_devices.h',
     'public/browser/media_device_id.cc',
     'public/browser/media_device_id.h',
-    'public/browser/media_devices_monitor.h',
     'public/browser/native_web_keyboard_event.h',
     'public/browser/navigation_controller.cc',
     'public/browser/navigation_controller.h',
@@ -761,7 +761,6 @@
     'browser/media/capture/web_contents_tracker.h',
     'browser/media/capture/web_contents_video_capture_device.cc',
     'browser/media/capture/web_contents_video_capture_device.h',
-    'browser/media/media_devices_monitor.cc',
     'browser/media/media_internals.cc',
     'browser/media/media_internals.h',
     'browser/media/media_internals_handler.cc',
@@ -973,6 +972,8 @@
     'browser/renderer_host/media/audio_sync_reader.h',
     'browser/renderer_host/media/device_request_message_filter.cc',
     'browser/renderer_host/media/device_request_message_filter.h',
+    'browser/renderer_host/media/media_capture_devices_impl.cc',
+    'browser/renderer_host/media/media_capture_devices_impl.h',
     'browser/renderer_host/media/media_stream_dispatcher_host.cc',
     'browser/renderer_host/media/media_stream_dispatcher_host.h',
     'browser/renderer_host/media/media_stream_manager.cc',
diff --git a/content/public/browser/media_capture_devices.h b/content/public/browser/media_capture_devices.h
new file mode 100644
index 0000000..925fff6
--- /dev/null
+++ b/content/public/browser/media_capture_devices.h
@@ -0,0 +1,32 @@
+// 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_
+#define CONTENT_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_
+
+#include "content/public/common/media_stream_request.h"
+
+namespace content {
+
+// This is a singleton class, used to get Audio/Video devices, it must be
+// called in UI thread.
+class CONTENT_EXPORT  MediaCaptureDevices {
+ public:
+  // Get signleton instance of MediaCaptureDevices.
+  static MediaCaptureDevices* GetInstance();
+
+  // Return all Audio/Video devices.
+  virtual const MediaStreamDevices& GetAudioCaptureDevices() = 0;
+  virtual const MediaStreamDevices& GetVideoCaptureDevices() = 0;
+
+ private:
+  // This interface should only be implemented inside content.
+  friend class MediaCaptureDevicesImpl;
+  MediaCaptureDevices() {}
+  virtual ~MediaCaptureDevices() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_
diff --git a/content/public/browser/media_devices_monitor.h b/content/public/browser/media_devices_monitor.h
deleted file mode 100644
index 044c8ad..0000000
--- a/content/public/browser/media_devices_monitor.h
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright (c) 2012 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.
-
-#ifndef CONTENT_PUBLIC_BROWSER_MEDIA_DEVICES_MONITOR_H_
-#define CONTENT_PUBLIC_BROWSER_MEDIA_DEVICES_MONITOR_H_
-
-#include "content/common/content_export.h"
-
-namespace content {
-
-// Called to ensure the MediaStreamManager has started monitoring the capture
-// devices, this will trigger OnAudioCaptureDevicesChanged() and
-// OnVideoCaptureDevicesChanged() callbacks.
-CONTENT_EXPORT void EnsureMonitorCaptureDevices();
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_MEDIA_DEVICES_MONITOR_H_
diff --git a/content/public/browser/media_observer.h b/content/public/browser/media_observer.h
index 20d47a5..dca5b85 100644
--- a/content/public/browser/media_observer.h
+++ b/content/public/browser/media_observer.h
@@ -16,12 +16,10 @@ namespace content {
 class MediaObserver {
  public:
   // Called when a audio capture device is plugged in or unplugged.
-  virtual void OnAudioCaptureDevicesChanged(
-      const MediaStreamDevices& devices) = 0;
+  virtual void OnAudioCaptureDevicesChanged() = 0;
 
   // Called when a video capture device is plugged in or unplugged.
-  virtual void OnVideoCaptureDevicesChanged(
-      const MediaStreamDevices& devices) = 0;
+  virtual void OnVideoCaptureDevicesChanged() = 0;
 
   // Called when a media request changes state.
   virtual void OnMediaRequestStateChanged(