Revert "Re-arm timer as necessary in MessageLoopFuchsia" (flutter#16568)

This reverts commit 8ec994b.

Author: George Wright

fml/message_loop_unittests.cc

@@ -10,7 +10,6 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/concurrent_message_loop.h"
 #include "flutter/fml/message_loop.h"
-#include "flutter/fml/message_loop_impl.h"
 #include "flutter/fml/synchronization/count_down_latch.h"
 #include "flutter/fml/synchronization/waitable_event.h"
 #include "flutter/fml/task_runner.h"
@@ -316,32 +315,3 @@ TEST(MessageLoop, CanCreateConcurrentMessageLoop) {
   latch.Wait();
   ASSERT_GE(thread_ids.size(), 1u);
 }
-
-TEST(MessageLoop, TIME_SENSITIVE(WakeUpTimersAreSingletons)) {
-  auto loop_impl = fml::MessageLoopImpl::Create();
-
-  const auto t1 = fml::TimeDelta::FromMilliseconds(10);
-  const auto t2 = fml::TimeDelta::FromMilliseconds(20);
-
-  const auto begin = fml::TimePoint::Now();
-
-  // Register a task scheduled for 10ms in the future. This schedules a
-  // WakeUp call on the MessageLoopImpl with that fml::TimePoint
-  loop_impl->PostTask(
-      [&]() {
-        auto delta = fml::TimePoint::Now() - begin;
-        auto ms = delta.ToMillisecondsF();
-        ASSERT_GE(ms, 10);
-        ASSERT_LE(ms, 25);
-
-        loop_impl->Terminate();
-      },
-      fml::TimePoint::Now() + t1);
-
-  // Call WakeUp manually to change the WakeUp time to the future. If the
-  // timer is correctly set up to be rearmed instead of a new timer scheduled,
-  // the above task will be executed at t2 instead of t1 now.
-  loop_impl->WakeUp(fml::TimePoint::Now() + t2);
-
-  loop_impl->Run();
-}

fml/platform/fuchsia/message_loop_fuchsia.cc

@@ -5,16 +5,13 @@
 #include "flutter/fml/platform/fuchsia/message_loop_fuchsia.h"
 
 #include <lib/async-loop/default.h>
+#include <lib/async/cpp/task.h>
 #include <lib/zx/time.h>
 
 namespace fml {
 
 MessageLoopFuchsia::MessageLoopFuchsia()
-    : loop_(&kAsyncLoopConfigAttachToCurrentThread) {
-  auto handler = [this](async_dispatcher_t* dispatcher, async::Task* task,
-                        zx_status_t status) { RunExpiredTasksNow(); };
-  task_.set_handler(handler);
-}
+    : loop_(&kAsyncLoopConfigAttachToCurrentThread) {}
 
 MessageLoopFuchsia::~MessageLoopFuchsia() = default;
 
@@ -33,12 +30,8 @@ void MessageLoopFuchsia::WakeUp(fml::TimePoint time_point) {
     due_time = zx::nsec((time_point - now).ToNanoseconds());
   }
 
-  std::scoped_lock lock(task_mutex_);
-
-  auto status = task_.Cancel();
-  FML_DCHECK(status == ZX_OK || status == ZX_ERR_NOT_FOUND);
-
-  status = task_.PostDelayed(loop_.dispatcher(), due_time);
+  auto status = async::PostDelayedTask(
+      loop_.dispatcher(), [this]() { RunExpiredTasksNow(); }, due_time);
   FML_DCHECK(status == ZX_OK);
 }
 

fml/platform/fuchsia/message_loop_fuchsia.h

@@ -6,7 +6,6 @@
 #define FLUTTER_FML_PLATFORM_FUCHSIA_MESSAGE_LOOP_FUCHSIA_H_
 
 #include <lib/async-loop/cpp/loop.h>
-#include <lib/async/cpp/task.h>
 
 #include "flutter/fml/macros.h"
 #include "flutter/fml/message_loop_impl.h"
@@ -26,8 +25,6 @@ class MessageLoopFuchsia : public MessageLoopImpl {
   void WakeUp(fml::TimePoint time_point) override;
 
   async::Loop loop_;
-  std::mutex task_mutex_;
-  async::Task task_;
 
   FML_FRIEND_MAKE_REF_COUNTED(MessageLoopFuchsia);
   FML_FRIEND_REF_COUNTED_THREAD_SAFE(MessageLoopFuchsia);