Fix leaks in WebAudio layout tests

When the context is closing, the nodes that were processing their
tails need to be stopped.  This disables the output of the node, which
might cause other nodes to disable their outputs, and these nodes are
placed on |finished_tail_processing_handlers_|.  These also need to be
handled when finishing tail processing.  So loop around processing
|finished_tail_processing_handlers_| and |tail_processing_handlers_|
until disabling of outputs no longer adds anything to either of these.


Bug: 832043, 828826
Test: run-webkit-tests --enable-leak-detection no longer detects leaks
Change-Id: I6ca195352b240d343095c208c9b70b0c5553c925
Reviewed-on: https://chromium-review.googlesource.com/1010833
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550468}

third_party/blink/renderer/modules/webaudio/deferred_task_handler.cc

@@ -328,14 +328,7 @@ void DeferredTaskHandler::DeleteHandlersOnMainThread() {
   DCHECK(IsMainThread());
   GraphAutoLocker locker(*this);
   deletable_orphan_handlers_.clear();
-  // Tail processing nodes have finished processing their tails so we need to
-  // disable their outputs to indicate to downstream nodes that they're done.
-  // This has to be done in the main thread because DisableOutputs() can causing
-  // summing juctions to go away, which must be done on the main thread.
-  for (auto& handler : finished_tail_processing_handlers_) {
-    handler->DisableOutputs();
-  }
-  finished_tail_processing_handlers_.clear();
+  DisableOutputsForTailProcessing();
 }
 
 void DeferredTaskHandler::ClearHandlersToBeDeleted() {
@@ -352,21 +345,44 @@ void DeferredTaskHandler::SetAudioThreadToCurrentThread() {
   ReleaseStore(&audio_thread_, thread);
 }
 
+void DeferredTaskHandler::DisableOutputsForTailProcessing() {
+  DCHECK(IsMainThread());
+  // Tail processing nodes have finished processing their tails so we need to
+  // disable their outputs to indicate to downstream nodes that they're done.
+  // This has to be done in the main thread because DisableOutputs() can cause
+  // summing juctions to go away, which must be done on the main thread.
+  for (auto& handler : finished_tail_processing_handlers_) {
+    handler->DisableOutputs();
+  }
+  finished_tail_processing_handlers_.clear();
+}
+
 void DeferredTaskHandler::FinishTailProcessing() {
   DCHECK(IsMainThread());
   // DisableOutputs must run with the graph lock.
   GraphAutoLocker locker(*this);
 
-  while (tail_processing_handlers_.size() > 0) {
-    // |DisableOutputs()| can modify |tail_processing_handlers_|, so
-    // swap it out before processing it.  And keep running this until
-    // nothing gets added to |tail_processing_handlers_|.
-    Vector<scoped_refptr<AudioHandler>> handlers;
-
-    handlers.swap(tail_processing_handlers_);
-    for (auto& handler : handlers)
-      handler->DisableOutputs();
-  }
+  // TODO(crbug.com/832200): Simplify this!
+
+  // |DisableOutputs()| can cause new handlers to start tail processing, which
+  // in turn can cause hte handler to want to disable outputs.  For the former
+  // case, the handler is added to |tail_processing_handlers_|.  In the latter
+  // case, the handler is added to |finished_tail_processing_handlers_|.  So, we
+  // need to loop around until these vectors are completely empty.
+  do {
+    while (tail_processing_handlers_.size() > 0) {
+      // |DisableOutputs()| can modify |tail_processing_handlers_|, so
+      // swap it out before processing it.  And keep running this until
+      // nothing gets added to |tail_processing_handlers_|.
+      Vector<scoped_refptr<AudioHandler>> handlers_to_be_disabled;
+
+      handlers_to_be_disabled.swap(tail_processing_handlers_);
+      for (auto& handler : handlers_to_be_disabled)
+        handler->DisableOutputs();
+    }
+    DisableOutputsForTailProcessing();
+  } while (tail_processing_handlers_.size() > 0 ||
+           finished_tail_processing_handlers_.size() > 0);
 }
 
 }  // namespace blink

third_party/blink/renderer/modules/webaudio/deferred_task_handler.h

@@ -118,6 +118,10 @@ class MODULES_EXPORT DeferredTaskHandler final
   // context is done.
   void FinishTailProcessing();
 
+  // For handlers that have finished processing their tail and require disabling
+  // the ouputs of the handler, we do that here.
+  void DisableOutputsForTailProcessing();
+
   //
   // Thread Safety and Graph Locking:
   //