Use SupportsWeakPtr for messaging from rendering thread to main thread

In cross-thread messaging, the associated execution context can be
already gone when a posted task is performed sometime later in the task
runner's queue.

By using WeakPtr, the task runner will not perform a scheduled task
in the queue when the target object is invalid.

Bug: 1057735
Change-Id: I3f218ad073ff5f6dcb08aba176d722c5c729316b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2086051Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747043}

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

@@ -178,7 +178,7 @@ void AudioWorkletHandler::SetProcessorOnRenderThread(
     PostCrossThreadTask(
         *main_thread_task_runner_, FROM_HERE,
         CrossThreadBindOnce(
-            &AudioWorkletHandler::NotifyProcessorError, WrapRefCounted(this),
+            &AudioWorkletHandler::NotifyProcessorError, AsWeakPtr(),
             AudioWorkletProcessorErrorState::kConstructionError));
   }
 }
@@ -193,7 +193,7 @@ void AudioWorkletHandler::FinishProcessorOnRenderThread() {
     PostCrossThreadTask(
         *main_thread_task_runner_, FROM_HERE,
         CrossThreadBindOnce(&AudioWorkletHandler::NotifyProcessorError,
-                            WrapRefCounted(this), error_state));
+                            AsWeakPtr(), error_state));
   }
 
   // TODO(hongchan): After this point, The handler has no more pending activity

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

@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_AUDIO_WORKLET_NODE_H_
 
 #include "base/memory/scoped_refptr.h"
+#include "base/memory/weak_ptr.h"
 #include "third_party/blink/renderer/bindings/modules/v8/v8_audio_worklet_node_options.h"
 #include "third_party/blink/renderer/modules/webaudio/audio_node.h"
 #include "third_party/blink/renderer/modules/webaudio/audio_param_map.h"
@@ -31,7 +32,9 @@ class ScriptState;
 //  AudioWorkletNode <-> AudioWorkletHandler <==|==>   AudioWorkletProcessor
 //   (JS interface)       (Renderer access)     |      (V8 audio processing)
 
-class AudioWorkletHandler final : public AudioHandler {
+class AudioWorkletHandler final
+    : public AudioHandler,
+      public base::SupportsWeakPtr<AudioWorkletHandler> {
  public:
   static scoped_refptr<AudioWorkletHandler> Create(
       AudioNode&,

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

@@ -340,7 +340,7 @@ void DeferredTaskHandler::RequestToDeleteHandlersOnMainThread() {
   PostCrossThreadTask(
       *task_runner_, FROM_HERE,
       CrossThreadBindOnce(&DeferredTaskHandler::DeleteHandlersOnMainThread,
-                          scoped_refptr<DeferredTaskHandler>(this)));
+                          AsWeakPtr()));
 }
 
 void DeferredTaskHandler::DeleteHandlersOnMainThread() {

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

@@ -28,6 +28,7 @@
 
 #include <atomic>
 #include "base/memory/scoped_refptr.h"
+#include "base/memory/weak_ptr.h"
 #include "third_party/blink/renderer/modules/modules_export.h"
 #include "third_party/blink/renderer/platform/heap/handle.h"
 #include "third_party/blink/renderer/platform/wtf/hash_set.h"
@@ -62,7 +63,8 @@ class AudioSummingJunction;
 // - GC happens and it collects the BaseAudioContext before the task execution.
 //
 class MODULES_EXPORT DeferredTaskHandler final
-    : public ThreadSafeRefCounted<DeferredTaskHandler> {
+    : public ThreadSafeRefCounted<DeferredTaskHandler>,
+      public base::SupportsWeakPtr<DeferredTaskHandler> {
  public:
   static scoped_refptr<DeferredTaskHandler> Create(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);

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

@@ -204,7 +204,7 @@ void ScriptProcessorHandler::Process(uint32_t frames_to_process) {
         PostCrossThreadTask(
             *task_runner_, FROM_HERE,
             CrossThreadBindOnce(&ScriptProcessorHandler::FireProcessEvent,
-                                WrapRefCounted(this), double_buffer_index_));
+                                AsWeakPtr(), double_buffer_index_));
       } else {
         // If this node is in the offline audio context, use the
         // waitable event to synchronize to the offline rendering thread.
@@ -215,7 +215,7 @@ void ScriptProcessorHandler::Process(uint32_t frames_to_process) {
             *task_runner_, FROM_HERE,
             CrossThreadBindOnce(
                 &ScriptProcessorHandler::FireProcessEventForOfflineAudioContext,
-                WrapRefCounted(this), double_buffer_index_,
+                AsWeakPtr(), double_buffer_index_,
                 CrossThreadUnretained(waitable_event.get())));
 
         // Okay to block the offline audio rendering thread since it is

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

@@ -28,6 +28,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_refptr.h"
+#include "base/memory/weak_ptr.h"
 #include "base/synchronization/waitable_event.h"
 #include "third_party/blink/renderer/bindings/core/v8/active_script_wrappable.h"
 #include "third_party/blink/renderer/modules/webaudio/audio_node.h"
@@ -51,7 +52,9 @@ class WaitableEvent;
 // periodically with an AudioProcessingEvent which has AudioBuffers for each
 // input and output.
 
-class ScriptProcessorHandler final : public AudioHandler {
+class ScriptProcessorHandler final
+    : public AudioHandler,
+      public base::SupportsWeakPtr<ScriptProcessorHandler> {
  public:
   static scoped_refptr<ScriptProcessorHandler> Create(
       AudioNode&,