Revert "Use ARGB8888 for a dummy buffer for protected content playbkack on ARC++"

This reverts commit eb0d6e13.

Reason for revert: This CL causes a crash on AMD device, b/117398307

Original change's description:
> Use ARGB8888 for a dummy buffer for protected content playbkack on ARC++
> 
> We have specified R8 format for a dummy buffer for protected content playback
> on ARC++.
> R8 format is not supported on exynos device. It leads crash on the devices.
> ARGB8888 should be used instead, which is widely supported on all Chrome OS
> device.
> 
> BUG=chromium:787660, chromium:887658
> TEST=No crash on peach_pit and Protected content playback on veyron_minnie and eve
> 
> Change-Id: Ia550277ad30a0e0fd814106a1610b59a1a86bb03
> Reviewed-on: https://chromium-review.googlesource.com/1242564
> Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
> Reviewed-by: Pawel Osciak <posciak@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#593842}

TBR=posciak@chromium.org,gurchetansingh@chromium.org,hiroh@chromium.org

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

Bug: chromium:787660, chromium:887658
Change-Id: I7cc4e8607b0dd267f73a2f32879abae74f9fa24e
Reviewed-on: https://chromium-review.googlesource.com/c/1282505Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599824}

components/arc/video_accelerator/protected_buffer_manager.cc

@@ -23,7 +23,7 @@ namespace arc {
 
 namespace {
 // Size of the pixmap to be used as the dummy handle for protected buffers.
-constexpr gfx::Size kDummyBufferSize(16, 16);
+constexpr gfx::Size kDummyBufferSize(32, 32);
 
 // Maximum number of concurrent ProtectedBufferAllocatorImpl instances.
 // Currently we have no way to know the resources of ProtectedBufferAllocator.
@@ -463,8 +463,8 @@ scoped_refptr<gfx::NativePixmap> ProtectedBufferManager::ImportDummyFd(
   ui::SurfaceFactoryOzone* factory = platform->GetSurfaceFactoryOzone();
   scoped_refptr<gfx::NativePixmap> pixmap =
       factory->CreateNativePixmapForProtectedBufferHandle(
-          gfx::kNullAcceleratedWidget, kDummyBufferSize,
-          gfx::BufferFormat::RGBA_8888, pixmap_handle);
+          gfx::kNullAcceleratedWidget, kDummyBufferSize, gfx::BufferFormat::R_8,
+          pixmap_handle);
   if (!pixmap) {
     VLOGF(1) << "Failed importing dummy handle";
     return nullptr;