webaudio: Remove unnecessary use of volatile and atomic operations in AudioHandler.

volatile does not add atomicity or thread safety, and is unnecessary here.

connection_ref_count_ is already accessed only while the graph mutex is held, so
there is no added benefit of atomic operations.

Change-Id: I69ecb8293360631872f8914b9bb013d06f49717d
Reviewed-on: https://chromium-review.googlesource.com/c/1348854Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610511}

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

@@ -32,7 +32,6 @@
 #include "third_party/blink/renderer/platform/bindings/exception_messages.h"
 #include "third_party/blink/renderer/platform/bindings/exception_state.h"
 #include "third_party/blink/renderer/platform/instance_counters.h"
-#include "third_party/blink/renderer/platform/wtf/atomics.h"
 
 #if DEBUG_AUDIONODE_REFERENCES
 #include <stdio.h>
@@ -466,7 +465,8 @@ void AudioHandler::DisableOutputs() {
 }
 
 void AudioHandler::MakeConnection() {
-  AtomicIncrement(&connection_ref_count_);
+  Context()->AssertGraphOwner();
+  connection_ref_count_++;
 
 #if DEBUG_AUDIONODE_REFERENCES
   fprintf(
@@ -508,8 +508,7 @@ void AudioHandler::BreakConnection() {
 
 void AudioHandler::BreakConnectionWithLock() {
   Context()->AssertGraphOwner();
-
-  AtomicDecrement(&connection_ref_count_);
+  connection_ref_count_--;
 
 #if DEBUG_AUDIONODE_REFERENCES
   fprintf(stderr,

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

@@ -263,7 +263,7 @@ class MODULES_EXPORT AudioHandler : public ThreadSafeRefCounted<AudioHandler> {
  private:
   void SetNodeType(NodeType);
 
-  volatile bool is_initialized_;
+  bool is_initialized_;
   NodeType node_type_;
 
   // The owner AudioNode. Accessed only on the main thread.
@@ -281,7 +281,7 @@ class MODULES_EXPORT AudioHandler : public ThreadSafeRefCounted<AudioHandler> {
   double last_processing_time_;
   double last_non_silent_time_;
 
-  volatile int connection_ref_count_;
+  int connection_ref_count_;
 
   bool is_disabled_;