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 91552055b963e99ba61b4bdf59393ad18a8e14f0..41696c66aa0db5ba1ff3484ade676a2f1768b2fd 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
@@ -127,6 +127,7 @@ bool GpuMemoryBufferImplSharedMemory::IsFormatSupported(Format format) {
     case DXT1:
     case DXT5:
     case ETC1:
+    case R_8:
     case RGBA_8888:
     case BGRA_8888:
     case YUV_420:
@@ -152,6 +153,7 @@ 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: