[vm] Remove hooks for the embedder to provide a task runner in lieu of the VM's thread pool.

This reverts commit dc3cf83bb6.

TEST=ci
Bug: https://github.com/dart-lang/sdk/issues/44228
Change-Id: Ia8da6424fd4ebc67e0a2a50e37b1930b4aea5628
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/231042
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/include/dart_api.h

@@ -849,7 +849,7 @@ typedef Dart_Handle (*Dart_GetVMServiceAssetsArchive)(void);
  * The current version of the Dart_InitializeFlags. Should be incremented every
  * time Dart_InitializeFlags changes in a binary incompatible way.
  */
-#define DART_INITIALIZE_PARAMS_CURRENT_VERSION (0x00000006)
+#define DART_INITIALIZE_PARAMS_CURRENT_VERSION (0x00000007)
 
 /** Forward declaration */
 struct Dart_CodeObserver;
@@ -875,50 +875,6 @@ typedef struct Dart_CodeObserver {
   Dart_OnNewCodeCallback on_new_code;
 } Dart_CodeObserver;
 
-typedef struct _Dart_Task* Dart_Task;
-typedef enum {
-  Dart_TaskPriority_Default,
-} Dart_TaskPriority;
-typedef struct {
-  /**
-   * Placeholder.
-   */
-  Dart_TaskPriority priority;
-  /**
-   * Time after which the task should run according to the clock of
-   * Dart_TimelineGetMicros.
-   */
-  int64_t time_point;
-} Dart_TaskData;
-/**
- * Callback provided by the embedder that is used by the VM to eventually run
- * various tasks. If no callback is provided, these tasks will run on a
- * VM-internal thread pool. This callback allows the embedder to make its own
- * choices around the scheduling of these tasks: when they run, how many threads
- * are servicing these tasks, the priorities of said threads, etc.
- * The callback can be invoked as early as during the Dart_Initialize call.
- *
- * \param post_task_data
- *     The data provided to Dart_InitializeParams.post_task_data.
- * \param task
- *     A task that should eventually be passed to Dart_RunTask.
- * \param task_data
- *     Hints about when the task should run.
- */
-typedef void (*Dart_PostTaskCallback)(void* post_task_data,
-                                      Dart_Task task,
-                                      Dart_TaskData task_data);
-
-/**
- * Runs a task given to the Dart_PostTaskCallback. Must not be called
- * synchronously in response to any callback from the VM. In particular, must
- * not be called synchronously by the implemention of a Dart native function
- * or Dart_Post_TaskCallback.
- *
- * Requires there to be no current isolate or isolate group.
- */
-DART_EXPORT void Dart_RunTask(Dart_Task task);
-
 /**
  * Optional callback provided by the embedder that is used by the VM to
  * implement registration of kernel blobs for the subsequent Isolate.spawnUri
@@ -1027,13 +983,6 @@ typedef struct {
    */
   Dart_CodeObserver* code_observer;
 
-  /**
-   * A task scheduling callback function. See Dart_PostTaskCallback.
-   */
-  Dart_PostTaskCallback post_task;
-
-  void* post_task_data;
-
   /**
    * Kernel blob registration callback function. See Dart_RegisterKernelBlobCallback.
    */

runtime/vm/dart.cc

@@ -69,8 +69,6 @@ Dart_FileWriteCallback Dart::file_write_callback_ = NULL;
 Dart_FileCloseCallback Dart::file_close_callback_ = NULL;
 Dart_EntropySource Dart::entropy_source_callback_ = NULL;
 Dart_GCEventCallback Dart::gc_event_callback_ = nullptr;
-Dart_PostTaskCallback Dart::post_task_callback_ = nullptr;
-void* Dart::post_task_data_ = nullptr;
 
 // Structure for managing read-only global handles allocation used for
 // creating global read-only handles that are pre created and initialized
@@ -283,8 +281,6 @@ char* Dart::DartInit(const Dart_InitializeParams* params) {
   SetFileCallbacks(params->file_open, params->file_read, params->file_write,
                    params->file_close);
   set_entropy_source_callback(params->entropy_source);
-  set_post_task_callback(params->post_task);
-  set_post_task_data(params->post_task_data);
   OS::Init();
   NOT_IN_PRODUCT(CodeObservers::Init());
   if (params->code_observer != nullptr) {
@@ -802,8 +798,6 @@ char* Dart::Cleanup() {
   Service::SetEmbedderStreamCallbacks(NULL, NULL);
 #endif  // !defined(PRODUCT) && !defined(DART_PRECOMPILED_RUNTIME)
   VirtualMemory::Cleanup();
-  post_task_callback_ = nullptr;
-  post_task_data_ = nullptr;
   return NULL;
 }
 

runtime/vm/dart.h

@@ -114,14 +114,6 @@ class Dart : public AllStatic {
   static void set_thread_exit_callback(Dart_ThreadExitCallback cback) {
     thread_exit_callback_ = cback;
   }
-  static Dart_PostTaskCallback post_task_callback() {
-    return post_task_callback_;
-  }
-  static void set_post_task_callback(Dart_PostTaskCallback cback) {
-    post_task_callback_ = cback;
-  }
-  static void* post_task_data() { return post_task_data_; }
-  static void set_post_task_data(void* data) { post_task_data_ = data; }
   static void SetFileCallbacks(Dart_FileOpenCallback file_open,
                                Dart_FileReadCallback file_read,
                                Dart_FileWriteCallback file_write,
@@ -179,8 +171,6 @@ class Dart : public AllStatic {
   static Dart_FileCloseCallback file_close_callback_;
   static Dart_EntropySource entropy_source_callback_;
   static Dart_GCEventCallback gc_event_callback_;
-  static Dart_PostTaskCallback post_task_callback_;
-  static void* post_task_data_;
 };
 
 }  // namespace dart

runtime/vm/dart_api_impl.cc

@@ -2047,16 +2047,6 @@ DART_EXPORT bool Dart_RunLoopAsync(bool errors_are_fatal,
   return true;
 }
 
-DART_EXPORT void Dart_RunTask(Dart_Task task) {
-  Thread* T = Thread::Current();
-  Isolate* I = T == nullptr ? nullptr : T->isolate();
-  CHECK_NO_ISOLATE(I);
-  API_TIMELINE_BEGIN_END(T);
-  ThreadPool::Task* task_impl = reinterpret_cast<ThreadPool::Task*>(task);
-  task_impl->Run();
-  delete task_impl;
-}
-
 DART_EXPORT Dart_Handle Dart_HandleMessage() {
   Thread* T = Thread::Current();
   Isolate* I = T->isolate();

runtime/vm/thread_pool.cc

@@ -82,22 +82,6 @@ void ThreadPool::Shutdown() {
 }
 
 bool ThreadPool::RunImpl(std::unique_ptr<Task> task) {
-  Dart_PostTaskCallback post_task = Dart::post_task_callback();
-  if (post_task != nullptr) {
-    {
-      MonitorLocker ml(&pool_monitor_);
-      if (shutting_down_) {
-        return false;
-      }
-    }
-    Dart_TaskData data;
-    data.priority = Dart_TaskPriority_Default;
-    data.time_point = 0;
-    post_task(Dart::post_task_data(),
-              reinterpret_cast<Dart_Task>(task.release()), data);
-    return true;
-  }
-
   Worker* new_worker = nullptr;
   {
     MonitorLocker ml(&pool_monitor_);