Revert "macOS HDR: Don't disable GMBs when display is HDR"

This reverts commit bbd20716.

Reason for revert: Tests failing on Mac Retina bots.
Bug: 1048497

Original change's description:
> macOS HDR: Don't disable GMBs when display is HDR
> 
> We always want HDR videos to use GMBs on macOS.
> 
> Bug: 976426
> Change-Id: I9cf36ef2d031ec99320dde8ce4599664df0fa6f4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2034903
> Reviewed-by: Miguel Casas <mcasas@chromium.org>
> Commit-Queue: ccameron <ccameron@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#737866}

TBR=ccameron@chromium.org,mcasas@chromium.org,dcastagna@chromium.org

Change-Id: I8cdb03e8c0029923ce2afbe89f2596e2e03a0a77
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 976426
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2035649Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738085}

content/renderer/media/gpu/gpu_video_accelerator_factories_impl.cc

@@ -323,7 +323,6 @@ GpuVideoAcceleratorFactoriesImpl::VideoFrameOutputFormat(
   auto capabilities = context_provider_->ContextCapabilities();
   const size_t bit_depth = media::BitDepth(pixel_format);
   if (bit_depth > 8) {
-#if !defined(OS_MACOSX)
     // If high bit depth rendering is enabled, bail here, otherwise try and use
     // XR30 storage, and if not and we support RG textures, use those, albeit at
     // a reduced bit depth of 8 bits per component.
@@ -331,7 +330,6 @@ GpuVideoAcceleratorFactoriesImpl::VideoFrameOutputFormat(
     // long as the hardware may support it https://crbug.com/798485.
     if (rendering_color_space_.IsHDR())
       return media::GpuVideoAcceleratorFactories::OutputFormat::UNDEFINED;
-#endif
 
 #if !defined(OS_WIN)
     // TODO(mcasas): enable Win https://crbug.com/803451.