Revert "[FileUtil] Test thread-safety of temp file APIs."

This reverts commit 20a5f39c.

Reason for revert: Breaking official linux builds.

Original change's description:
> [FileUtil] Test thread-safety of temp file APIs.
> 
> Ruling out https://crbug.com/826408#c17 as the source of the issue.
> 
> R=​thestig@chromium.org
> 
> Bug: 826408
> Change-Id: I00396084d674fa2f700eb917300280b6eed1684d
> Reviewed-on: https://chromium-review.googlesource.com/1072030
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#561666}

TBR=gab@chromium.org,thestig@chromium.org

Change-Id: Icc838da2c247563b94c5e6508c8c268df68f3ce9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 826408, 846563
Reviewed-on: https://chromium-review.googlesource.com/1072966Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Michael Moss <mmoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561772}

base/files/file_util_unittest.cc

@@ -4,7 +4,6 @@
 
 #include <stddef.h>
 #include <stdint.h>
-#include <stdio.h>
 
 #include <algorithm>
 #include <fstream>
@@ -26,7 +25,6 @@
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/files/scoped_temp_dir.h"
-#include "base/guid.h"
 #include "base/macros.h"
 #include "base/path_service.h"
 #include "base/strings/string_util.h"
@@ -36,7 +34,6 @@
 #include "base/test/test_file_util.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/platform_thread.h"
-#include "base/threading/thread.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/multiprocess_func_list.h"
@@ -3640,63 +3637,6 @@ TEST_F(FileUtilTest, NonExistentContentUriTest) {
 }
 #endif
 
-// Test that temp files obtained racily are all unique (no interference between
-// threads). Mimics file operations in DoLaunchChildTestProcess() to rule out
-// thread-safety issues @ https://crbug.com/826408#c17.
-TEST(FileUtilMultiThreadedTest, MultiThreadedTempFiles) {
-  constexpr int kNumThreads = 64;
-  constexpr int kNumWritesPerThread = 32;
-
-  std::unique_ptr<Thread> threads[kNumThreads];
-  for (auto& thread : threads) {
-    thread = std::make_unique<Thread>("test worker");
-    thread->Start();
-  }
-
-  // Wait until all threads are started for max parallelism.
-  for (auto& thread : threads)
-    thread->WaitUntilThreadStarted();
-
-  const RepeatingClosure open_write_close_read = BindRepeating([]() {
-    FilePath output_filename;
-    ScopedFILE output_file(CreateAndOpenTemporaryFile(&output_filename));
-    EXPECT_TRUE(output_file);
-
-    const std::string content = GenerateGUID();
-#if defined(OS_WIN)
-    HANDLE handle =
-        reinterpret_cast<HANDLE>(_get_osfhandle(_fileno(output_file.get())));
-    DWORD bytes_written = 0;
-    ::WriteFile(handle, content.c_str(), content.length(), &bytes_written,
-                NULL);
-    EXPECT_EQ(content.length(), bytes_written);
-#else
-    ::write(::fileno(output_file.get()), content.c_str(), content.length());
-#endif
-    ::fflush(output_file.get());
-    output_file.reset();
-
-    std::string output_file_contents;
-    EXPECT_TRUE(ReadFileToString(output_filename, &output_file_contents))
-        << output_filename;
-
-    EXPECT_EQ(content, output_file_contents);
-
-    DeleteFile(output_filename, false);
-  });
-
-  // Post tasks to each thread in a round-robin fashion to ensure as much
-  // parallelism as possible.
-  for (int i = 0; i < kNumWritesPerThread; ++i) {
-    for (auto& thread : threads) {
-      thread->task_runner()->PostTask(FROM_HERE, open_write_close_read);
-    }
-  }
-
-  for (auto& thread : threads)
-    thread->Stop();
-}
-
 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
 
 TEST(ScopedFD, ScopedFDDoesClose) {