Simplify locking in HRTFDatabaseLoader

third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp

Index: third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp
diff --git a/third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp b/third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp
index 223293a7ed3a8adaab4ace0899f7ef82ce3db39c..601ae5119be969b5a49bfee9ab170dbf3d8db5ec 100644
--- a/third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp
+++ b/third_party/WebKit/Source/platform/audio/HRTFDatabaseLoader.cpp
@@ -78,31 +78,37 @@ void HRTFDatabaseLoader::loadTask()
 {
     ASSERT(!isMainThread());

[hongchan, 2016/07/15 16:19:00]

I don't mind changing this to DCHECK.

 
-    {
-        MutexLocker locker(m_lock);
-        if (!m_hrtfDatabase) {
-            // Load the default HRTF database.
-            m_hrtfDatabase = HRTFDatabase::create(m_databaseSampleRate);
-        }
-    }
+    DCHECK(!m_hrtfDatabase);
+
+    MutexLocker locker(m_lock);
+    // Load the default HRTF database.
+    m_hrtfDatabase = HRTFDatabase::create(m_databaseSampleRate);
 }
 
 void HRTFDatabaseLoader::loadAsynchronously()
 {
     ASSERT(isMainThread());
 
-    MutexLocker locker(m_lock);
-    if (!m_hrtfDatabase && !m_thread) {
-        // Start the asynchronous database loading process.
-        m_thread = wrapUnique(Platform::current()->createThread("HRTF database loader"));
-        // TODO(alexclarke): Should this be posted as a loading task?
-        m_thread->getWebTaskRunner()->postTask(BLINK_FROM_HERE, crossThreadBind(&HRTFDatabaseLoader::loadTask, crossThreadUnretained(this)));
-    }
+    DCHECK(!m_hrtfDatabase);
+    DCHECK(!m_thread);
+
+    // Start the asynchronous database loading process.
+    m_thread = wrapUnique(Platform::current()->createThread("HRTF database loader"));

[hongchan, 2016/07/15 16:19:00]

Is wrapUnique necessary here?

[Raymond Toy, 2016/07/15 16:27:07]

Don't know. I didn't change this.

+    // TODO(alexclarke): Should this be posted as a loading task?
+    m_thread->getWebTaskRunner()->postTask(BLINK_FROM_HERE, crossThreadBind(&HRTFDatabaseLoader::loadTask, crossThreadUnretained(this)));
 }
 
-bool HRTFDatabaseLoader::isLoaded()
+HRTFDatabase* HRTFDatabaseLoader::database()
 {
-    MutexLocker locker(m_lock);
+    DCHECK(!isMainThread());
+
+    // Seeing that this is only called from the audio thread, we can't block.
+    // It's ok to return false if we can't get the lock.
+    MutexTryLocker tryLocker(m_lock);

[hongchan, 2016/07/15 16:19:00]

How is this tryLocker is connected to the audio thread's lock? This lock is only
valid for the lock at line 83. No?

[Raymond Toy, 2016/07/15 16:27:07]

Yeah, this is for protecting access to m_hrtfDatabase, which is what we want to
protect.

+
+    if (tryLocker.locked())
+        return nullptr;
+
     return m_hrtfDatabase.get();
 }