Add R_8 GPU memory buffers format.

ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc

Index: ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc
diff --git a/ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc b/ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc
index 38667e51e180f2d306fc50ec87e8994da9d88e1f..19c52d39aa5bfa756794a67988f2697b2eeff9f6 100644
--- a/ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc
+++ b/ui/ozone/gpu/gpu_memory_buffer_factory_ozone_native_buffer.cc
@@ -95,6 +95,7 @@ SurfaceFactoryOzone::BufferFormat GetOzoneFormatFor(
     case gfx::GpuMemoryBuffer::DXT1:
     case gfx::GpuMemoryBuffer::DXT5:
     case gfx::GpuMemoryBuffer::ETC1:
+    case gfx::GpuMemoryBuffer::R_8:
     case gfx::GpuMemoryBuffer::BGRA_8888:
       NOTREACHED();
       return SurfaceFactoryOzone::RGBA_8888;