Revert "media/gpu/test/VFValidator: Workaround the buffer synchronization problem on intel 3.18"

This reverts commit 276dd2ba.

Reason for revert: The root cause of the synchronization is fixed.
Removes this workaround.

Original change's description:
> media/gpu/test/VFValidator: Workaround the buffer synchronization problem on intel 3.18
>
> There is a synchronization problem on the mapped buffer on intel
> skylake devices. This is due to some missing 9165 patches in kernel
> 3.18, and thus will be fixed if the kernel is upreved to 4.4 or
> newer. This bug causes a decoded content validation failure in
> video_decode_accelerator_tests.
> This is a workaround to this bug; usleep() is added after the
> buffer is mapped and before the frame validation if the kernel
> version is 3.18 and the processor is Skylake.
>
> Bug: b:149808895
> Test: video_decode_accelerator_tests on sentry
> Change-Id: Ib77ebe0b83834e4d91bc994cbe6912348862e021
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2371724
> Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
> Reviewed-by: Miguel Casas <mcasas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#801614}

TBR=mcasas@chromium.org,hiroh@chromium.org,andrescj@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: b:149808895
Change-Id: Id0f1bdcc486effef2c6d3fd64275d71051020028
Test: None
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631645Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843919}

media/gpu/test/video_frame_validator.cc

@@ -5,19 +5,14 @@
 #include "media/gpu/test/video_frame_validator.h"
 
 #include "base/bind.h"
-#include "base/cpu.h"
 #include "base/files/file.h"
 #include "base/hash/md5.h"
 #include "base/memory/ptr_util.h"
-#include "base/no_destructor.h"
 #include "base/numerics/safe_conversions.h"
-#include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
-#include "base/system/sys_info.h"
 #include "build/build_config.h"
 #include "build/chromeos_buildflags.h"
 #include "media/base/video_frame.h"
-#include "media/gpu/buildflags.h"
 #include "media/gpu/macros.h"
 #include "media/gpu/test/image_quality_metrics.h"
 #include "media/gpu/test/video_test_helpers.h"
@@ -225,27 +220,6 @@ std::unique_ptr<VideoFrameValidator::MismatchedFrameInfo>
 MD5VideoFrameValidator::Validate(scoped_refptr<const VideoFrame> frame,
                                  size_t frame_index) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(validator_thread_sequence_checker_);
-#if BUILDFLAG(IS_CHROMEOS_ASH) || BUILDFLAG(IS_CHROMEOS_LACROS)
-  // b/149808895: There is a bug in the synchronization on mapped buffers, which
-  // causes the frame validation failure. The bug is due to some missing i915
-  // patches in kernel v3.18. The bug will be fixed if the kernel is upreved to
-  // v4.4 or newer. Inserts usleep as a short term workaround to the
-  // synchronization bug until the kernel uprev is complete for all the v3.18
-  // devices. Since this bug only occurs in Skylake just because they are 3.18
-  // devices, we also filter by the processor.
-  const static std::string kernel_version = base::SysInfo::KernelVersion();
-  if (base::StartsWith(kernel_version, "3.18")) {
-    constexpr int kPentiumAndLaterFamily = 0x06;
-    constexpr int kSkyLakeModelId = 0x5E;
-    constexpr int kSkyLake_LModelId = 0x4E;
-    static base::NoDestructor<base::CPU> cpuid;
-    static bool is_skylake = cpuid->family() == kPentiumAndLaterFamily &&
-                             (cpuid->model() == kSkyLakeModelId ||
-                              cpuid->model() == kSkyLake_LModelId);
-    if (is_skylake)
-      usleep(10);
-  }
-#endif  // BUILDFLAG(IS_CHROMEOS_ASH) || BUILDFLAG(IS_CHROMEOS_LACROS)
   if (frame->format() != validation_format_) {
     frame = ConvertVideoFrame(frame.get(), validation_format_);
   }