Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/DeferredTaskHandler.cpp

Index: Source/modules/webaudio/DeferredTaskHandler.cpp
diff --git a/Source/modules/webaudio/DeferredTaskHandler.cpp b/Source/modules/webaudio/DeferredTaskHandler.cpp
index c2605c157caa2787a5da09895322d8aa52a7ff66..f62cc9a24f15da0f28e2199afdde4fd9b647aa9b 100644
--- a/Source/modules/webaudio/DeferredTaskHandler.cpp
+++ b/Source/modules/webaudio/DeferredTaskHandler.cpp
@@ -42,6 +42,14 @@ void DeferredTaskHandler::lock()
     m_contextGraphMutex.lock();
 }
 
+void DeferredTaskHandler::forceLock()
+{
+    // This allows the regular lock in offline audio rendering. It is okay to
+    // lock the offline audio render thread because it is not real-time thread.
+    ASSERT(!isMainThread());
+    m_contextGraphMutex.lock();
+}
+
 bool DeferredTaskHandler::tryLock()
 {
     // Try to catch cases of using try lock on main thread