Remove redundant thread checker in FML. (#8053)

There is already fml/memory/thread_checker.h

ci/licenses_golden/licenses_flutter

@@ -219,8 +219,6 @@ FILE: ../../../flutter/fml/synchronization/shared_mutex_std.cc
 FILE: ../../../flutter/fml/synchronization/shared_mutex_std.h
 FILE: ../../../flutter/fml/synchronization/thread_annotations.h
 FILE: ../../../flutter/fml/synchronization/thread_annotations_unittest.cc
-FILE: ../../../flutter/fml/synchronization/thread_checker.h
-FILE: ../../../flutter/fml/synchronization/thread_checker_unittest.cc
 FILE: ../../../flutter/fml/synchronization/waitable_event.cc
 FILE: ../../../flutter/fml/synchronization/waitable_event.h
 FILE: ../../../flutter/fml/synchronization/waitable_event_unittest.cc

fml/BUILD.gn

@@ -50,7 +50,6 @@ source_set("fml") {
     "synchronization/count_down_latch.h",
     "synchronization/shared_mutex.h",
     "synchronization/thread_annotations.h",
-    "synchronization/thread_checker.h",
     "synchronization/waitable_event.cc",
     "synchronization/waitable_event.h",
     "task_runner.cc",
@@ -188,7 +187,6 @@ executable("fml_unittests") {
     "string_view_unittest.cc",
     "synchronization/count_down_latch_unittests.cc",
     "synchronization/thread_annotations_unittest.cc",
-    "synchronization/thread_checker_unittest.cc",
     "synchronization/waitable_event_unittest.cc",
     "thread_local_unittests.cc",
     "thread_unittests.cc",

fml/synchronization/thread_checker.h

-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// A class for checking that the current thread is/isn't the same as an initial
-// thread.
-
-#ifndef FLUTTER_FML_SYNCHRONIZATION_THREAD_CHECKER_H_
-#define FLUTTER_FML_SYNCHRONIZATION_THREAD_CHECKER_H_
-
-#include "flutter/fml/build_config.h"
-
-#if defined(OS_WIN)
-#include <windows.h>
-#else
-#include <pthread.h>
-#endif
-
-#include "flutter/fml/logging.h"
-#include "flutter/fml/macros.h"
-
-namespace fml {
-
-// A simple class that records the identity of the thread that it was created
-// on, and at later points can tell if the current thread is the same as its
-// creation thread. This class is thread-safe.
-//
-// Note: Unlike Chromium's |base::ThreadChecker|, this is *not* Debug-only (so
-// #ifdef it out if you want something Debug-only). (Rationale: Having a
-// |CalledOnValidThread()| that lies in Release builds seems bad. Moreover,
-// there's a small space cost to having even an empty class. )
-class ThreadChecker final {
- public:
-#if defined(OS_WIN)
-  ThreadChecker() : self_(GetCurrentThreadId()) {}
-  ~ThreadChecker() {}
-
-  bool IsCreationThreadCurrent() const { return GetCurrentThreadId() == self_; }
-
- private:
-  const DWORD self_;
-
-#else
-  ThreadChecker() : self_(pthread_self()) {}
-  ~ThreadChecker() {}
-
-  // Returns true if the current thread is the thread this object was created
-  // on and false otherwise.
-  bool IsCreationThreadCurrent() const {
-    return !!pthread_equal(pthread_self(), self_);
-  }
-
- private:
-  const pthread_t self_;
-#endif
-
-  FML_DISALLOW_COPY_AND_ASSIGN(ThreadChecker);
-};
-
-#ifndef NDEBUG
-#define FML_DECLARE_THREAD_CHECKER(c) fml::ThreadChecker c
-#define FML_DCHECK_CREATION_THREAD_IS_CURRENT(c) \
-  FML_DCHECK((c).IsCreationThreadCurrent())
-#else
-#define FML_DECLARE_THREAD_CHECKER(c)
-#define FML_DCHECK_CREATION_THREAD_IS_CURRENT(c) ((void)0)
-#endif
-
-}  // namespace fml
-
-#endif  // FLUTTER_FML_SYNCHRONIZATION_THREAD_CHECKER_H_

fml/synchronization/thread_checker_unittest.cc

-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "flutter/fml/synchronization/thread_checker.h"
-
-#include <thread>
-
-#include "gtest/gtest.h"
-
-namespace fml {
-namespace {
-
-TEST(ThreadCheckerTest, SameThread) {
-  ThreadChecker checker;
-  EXPECT_TRUE(checker.IsCreationThreadCurrent());
-}
-
-// Note: This test depends on |std::thread| being compatible with
-// |pthread_self()|.
-TEST(ThreadCheckerTest, DifferentThreads) {
-  ThreadChecker checker1;
-  EXPECT_TRUE(checker1.IsCreationThreadCurrent());
-
-  std::thread thread([&checker1]() {
-    ThreadChecker checker2;
-    EXPECT_TRUE(checker2.IsCreationThreadCurrent());
-    EXPECT_FALSE(checker1.IsCreationThreadCurrent());
-  });
-  thread.join();
-
-  // Note: Without synchronization, we can't look at |checker2| from the main
-  // thread.
-}
-
-}  // namespace
-}  // namespace fml