Merge M56: "Remove unnecessary lock on setClient()."

media/blink/webaudiosourceprovider_impl.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 "media/blink/webaudiosourceprovider_impl.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 87 matching lines @@
       client_(nullptr),
       sink_(sink),
       tee_filter_(new TeeFilter()),
       weak_factory_(this) {}
 
 WebAudioSourceProviderImpl::~WebAudioSourceProviderImpl() {
 }
 
 void WebAudioSourceProviderImpl::setClient(
     blink::WebAudioSourceProviderClient* client) {
+  // Skip taking the lock if unnecessary. This function is the only setter for
+  // |client_| so it's safe to check |client_| outside of the lock.
+  if (client_ == client)
+    return;
+
   base::AutoLock auto_lock(sink_lock_);
-  if (client && client != client_) {
+  if (client) {
     // Detach the audio renderer from normal playback.
     sink_->Stop();
 
     // The client will now take control by calling provideInput() periodically.
     client_ = client;
 
     set_format_cb_ = BindToCurrentLoop(base::Bind(
         &WebAudioSourceProviderImpl::OnSetFormat, weak_factory_.GetWeakPtr()));
 
     // If |tee_filter_| is Initialize()d - then run |set_format_cb_| to send
     // |client_| the current format info. Otherwise |set_format_cb_| will get
     // called when Initialize() is called. Note: Always using |set_format_cb_|
     // ensures we have the same locking order when calling into |client_|.
     if (tee_filter_->IsInitialized())
       base::ResetAndReturn(&set_format_cb_).Run();
-  } else if (!client && client_) {
-    // Restore normal playback.
-    client_ = nullptr;
-    sink_->SetVolume(volume_);
-    if (state_ >= kStarted)
-      sink_->Start();
-    if (state_ >= kPlaying)
-      sink_->Play();
+    return;
   }
+
+  // Restore normal playback.
+  client_ = nullptr;
+  sink_->SetVolume(volume_);
+  if (state_ >= kStarted)
+    sink_->Start();
+  if (state_ >= kPlaying)
+    sink_->Play();
 }
 
 void WebAudioSourceProviderImpl::provideInput(
     const WebVector<float*>& audio_data, size_t number_of_frames) {
   if (!bus_wrapper_ ||
       static_cast<size_t>(bus_wrapper_->channels()) != audio_data.size()) {
     bus_wrapper_ = AudioBus::CreateWrapper(static_cast<int>(audio_data.size()));
   }
 
   const int incoming_number_of_frames = static_cast<int>(number_of_frames);
@@ skipping 140 matching lines @@
 
   return num_rendered_frames;
 }
 
 void WebAudioSourceProviderImpl::TeeFilter::OnRenderError() {
   DCHECK(IsInitialized());
   renderer_->OnRenderError();
 }
 
 }  // namespace media