Use the browser UI thread for audio on OSX.

media/audio/mac/audio_device_listener_mac.cc

Index: media/audio/mac/audio_device_listener_mac.cc
diff --git a/media/audio/mac/audio_device_listener_mac.cc b/media/audio/mac/audio_device_listener_mac.cc
index 0c33d10c2fa330591490cff26e8b72e96170fe83..34c0a168327e3f1d8171148815facc45cfb78d7a 100644
--- a/media/audio/mac/audio_device_listener_mac.cc
+++ b/media/audio/mac/audio_device_listener_mac.cc
@@ -7,7 +7,6 @@
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
-#include "base/mac/libdispatch_task_runner.h"
 #include "base/mac/mac_logging.h"
 #include "base/mac/mac_util.h"
 #include "base/message_loop.h"
@@ -16,74 +15,6 @@
 
 namespace media {
 
-// TaskObserver which guarantees that dispatch queue operations such as property
-// listener callbacks are mutually exclusive to operations on the audio thread.
-// TODO(dalecurtis): Instead we should replace the main thread with a dispatch
-// queue.  See http://crbug.com/158170.
-class ExclusiveDispatchQueueTaskObserver
-    : public base::MessageLoop::TaskObserver {
- public:
-  ExclusiveDispatchQueueTaskObserver()
-      : property_listener_queue_(new base::mac::LibDispatchTaskRunner(
-            "com.google.chrome.AudioPropertyListenerQueue")),
-        queue_(property_listener_queue_->GetDispatchQueue()),
-        message_loop_(base::MessageLoop::current()) {
-    // If we're currently on the thread, fire the suspend operation so we don't
-    // end up with an unbalanced resume.
-    if (message_loop_->message_loop_proxy()->BelongsToCurrentThread())
-      SuspendDispatchQueue();
-
-    message_loop_->AddTaskObserver(this);
-  }
-
-  virtual ~ExclusiveDispatchQueueTaskObserver() {
-    message_loop_->RemoveTaskObserver(this);
-
-    // If we're currently on the thread, fire the resume operation so we don't
-    // end up with an unbalanced suspend.
-    if (message_loop_->message_loop_proxy()->BelongsToCurrentThread())
-      ResumeDispatchQueue();
-
-    // This will hang if any listeners are still registered with the queue.
-    property_listener_queue_->Shutdown();
-  }
-
-  virtual void WillProcessTask(const base::PendingTask& pending_task) OVERRIDE {
-    SuspendDispatchQueue();
-  }
-
-  virtual void DidProcessTask(const base::PendingTask& pending_task) OVERRIDE {
-    ResumeDispatchQueue();
-  }
-
-  dispatch_queue_t dispatch_queue() const {
-    return queue_;
-  }
-
- private:
-  // Issue a synchronous suspend operation.  Benchmarks on a retina 10.8.2
-  // machine show this takes < 20us on average.  dispatch_suspend() is an
-  // asynchronous operation so we need to issue it inside of a synchronous block
-  // to ensure it completes before WillProccesTask() completes.
-  void SuspendDispatchQueue() {
-    dispatch_sync(queue_, ^{
-        dispatch_suspend(queue_);
-    });
-  }
-
-  // Issue an asynchronous resume operation.  Benchmarks on a retina 10.8.2
-  // machine show this takes < 10us on average.
-  void ResumeDispatchQueue() {
-    dispatch_resume(queue_);
-  }
-
-  scoped_refptr<base::mac::LibDispatchTaskRunner> property_listener_queue_;
-  const dispatch_queue_t queue_;
-  base::MessageLoop* message_loop_;
-
-  DISALLOW_COPY_AND_ASSIGN(ExclusiveDispatchQueueTaskObserver);
-};
-
 // Property address to monitor for device changes.
 const AudioObjectPropertyAddress
 AudioDeviceListenerMac::kDeviceChangePropertyAddress = {
@@ -106,7 +37,10 @@ OSStatus AudioDeviceListenerMac::OnDefaultDeviceChanged(
         addresses[i].mScope == kDeviceChangePropertyAddress.mScope &&
         addresses[i].mElement == kDeviceChangePropertyAddress.mElement &&
         context) {
-      static_cast<AudioDeviceListenerMac*>(context)->listener_cb_.Run();
+      AudioDeviceListenerMac* p_this =
+          static_cast<AudioDeviceListenerMac*>(context);
+      DCHECK(p_this->thread_checker_.CalledOnValidThread());
+      p_this->listener_cb_.Run();
       break;
     }
   }
@@ -114,72 +48,16 @@ OSStatus AudioDeviceListenerMac::OnDefaultDeviceChanged(
   return noErr;
 }
 
-AudioDeviceListenerMac::AudioDeviceListenerMac(const base::Closure& listener_cb)
-    : listener_block_(NULL),
-      add_listener_block_func_(NULL),
-      remove_listener_block_func_(NULL) {
-  // Device changes are hard, lets go shopping!  Sadly OSX does not handle
-  // property listener callbacks in a thread safe manner.  On 10.6 we can set
-  // kAudioHardwarePropertyRunLoop to account for this.  On 10.7 this is broken
-  // and we need to create a dispatch queue to drive callbacks.  However code
-  // running on the dispatch queue must be mutually exclusive with code running
-  // on the audio thread.   ExclusiveDispatchQueueTaskObserver works around this
-  // by pausing and resuming the dispatch queue before and after each pumped
-  // task.  This is not ideal and long term we should replace the audio thread
-  // on OSX with a dispatch queue.  See http://crbug.com/158170 for discussion.
-  // TODO(dalecurtis): Does not fix the cases where
-  // GetDefaultOutputStreamParameters() are called by the browser process.
-  // These are one time events due to renderer side cache and thus unlikely to
-  // occur at the same time as a device callback.  Should be fixed along with
-  // http://crbug.com/137326 using a forced PostTask.
-  if (base::mac::IsOSLionOrLater()) {
-    if (!LoadAudioObjectPropertyListenerBlockFunctions())
-      return;
-
-    task_observer_.reset(new ExclusiveDispatchQueueTaskObserver());
-    listener_block_ = Block_copy(^(
-        UInt32 num_addresses, const AudioObjectPropertyAddress addresses[]) {
-            OnDefaultDeviceChanged(
-                kAudioObjectSystemObject, num_addresses, addresses, this);
-        });
-
-    OSStatus result = add_listener_block_func_(
-        kAudioObjectSystemObject, &kDeviceChangePropertyAddress,
-        task_observer_->dispatch_queue(), listener_block_);
-
-    if (result != noErr) {
-      task_observer_.reset();
-      Block_release(listener_block_);
-      listener_block_ = NULL;
-      OSSTATUS_DLOG(ERROR, result)
-          << "AudioObjectAddPropertyListenerBlock() failed!";
-      return;
-    }
-  } else {
-    const AudioObjectPropertyAddress kRunLoopAddress = {
-      kAudioHardwarePropertyRunLoop,
-      kAudioObjectPropertyScopeGlobal,
-      kAudioObjectPropertyElementMaster
-    };
-
-    CFRunLoopRef run_loop = CFRunLoopGetCurrent();
-    UInt32 size = sizeof(CFRunLoopRef);
-    OSStatus result = AudioObjectSetPropertyData(
-        kAudioObjectSystemObject, &kRunLoopAddress, 0, 0, size, &run_loop);
-    if (result != noErr) {
-      OSSTATUS_DLOG(ERROR, result) << "Failed to set property listener thread.";
-      return;
-    }
-
-    result = AudioObjectAddPropertyListener(
-        kAudioObjectSystemObject, &kDeviceChangePropertyAddress,
-        &AudioDeviceListenerMac::OnDefaultDeviceChanged, this);
+AudioDeviceListenerMac::AudioDeviceListenerMac(
+    const base::Closure& listener_cb) {
+  OSStatus result = AudioObjectAddPropertyListener(
+      kAudioObjectSystemObject, &kDeviceChangePropertyAddress,
+      &AudioDeviceListenerMac::OnDefaultDeviceChanged, this);
 
-    if (result != noErr) {
-      OSSTATUS_DLOG(ERROR, result)
-          << "AudioObjectAddPropertyListener() failed!";
-      return;
-    }
+  if (result != noErr) {
+    OSSTATUS_DLOG(ERROR, result)
+        << "AudioObjectAddPropertyListener() failed!";
+    return;
   }
 
   listener_cb_ = listener_cb;
@@ -190,20 +68,6 @@ AudioDeviceListenerMac::~AudioDeviceListenerMac() {
   if (listener_cb_.is_null())
     return;
 
-  if (task_observer_) {
-    OSStatus result = remove_listener_block_func_(
-        kAudioObjectSystemObject, &kDeviceChangePropertyAddress,
-        task_observer_->dispatch_queue(), listener_block_);
-
-    OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
-        << "AudioObjectRemovePropertyListenerBlock() failed!";
-
-    // Task observer will wait for all outstanding callbacks to complete.
-    task_observer_.reset();
-    Block_release(listener_block_);
-    return;
-  }
-
   // Since we're running on the same CFRunLoop, there can be no outstanding
   // callbacks in flight.
   OSStatus result = AudioObjectRemovePropertyListener(
@@ -213,35 +77,4 @@ AudioDeviceListenerMac::~AudioDeviceListenerMac() {
       << "AudioObjectRemovePropertyListener() failed!";
 }
 
-bool AudioDeviceListenerMac::LoadAudioObjectPropertyListenerBlockFunctions() {
-  // Dynamically load required block functions.
-  // TODO(dalecurtis): Remove once the deployment target is > 10.6.
-  std::string error;
-  base::NativeLibrary core_audio = base::LoadNativeLibrary(base::FilePath(
-      "/System/Library/Frameworks/CoreAudio.framework/Versions/Current/"
-      "CoreAudio"), &error);
-  if (!error.empty()) {
-    LOG(ERROR) << "Could not open CoreAudio library: " << error;
-    return false;
-  }
-
-  core_audio_lib_.Reset(core_audio);
-  add_listener_block_func_ =
-      reinterpret_cast<AudioObjectPropertyListenerBlockT>(
-          core_audio_lib_.GetFunctionPointer(
-              "AudioObjectAddPropertyListenerBlock"));
-  remove_listener_block_func_ =
-      reinterpret_cast<AudioObjectPropertyListenerBlockT>(
-          core_audio_lib_.GetFunctionPointer(
-              "AudioObjectRemovePropertyListenerBlock"));
-
-  // If either function failed to load, skip listener registration.
-  if (!add_listener_block_func_ || !remove_listener_block_func_) {
-    DLOG(ERROR) << "Failed to load audio property listener block functions!";
-    return false;
-  }
-
-  return true;
-}
-
 }  // namespace media