Add R_8 GPU memory buffers format.

content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc

Index: content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
diff --git a/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc b/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
index 3d3aee965a3d5aaa526538d9b1aff7d6923e1d24..fdf33197cf036a33d6c20a26f8757f8de2816bff 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
@@ -122,6 +122,7 @@ bool GpuMemoryBufferImplSharedMemory::IsFormatSupported(Format format) {
     case DXT1:
     case DXT5:
     case ETC1:
+    case R_8:
     case RGBA_8888:
     case BGRA_8888:
       return true;
@@ -146,6 +147,7 @@ bool GpuMemoryBufferImplSharedMemory::IsSizeValidForFormat(
       // Compressed images must have a width and height that's evenly divisible
       // by the block size.
       return size.width() % 4 == 0 && size.height() % 4 == 0;
+    case R_8:
     case RGBA_8888:
     case BGRA_8888:
     case RGBX_8888: