Add R_8 GPU memory buffers format.

cc/test/test_gpu_memory_buffer_manager.cc

Index: cc/test/test_gpu_memory_buffer_manager.cc
diff --git a/cc/test/test_gpu_memory_buffer_manager.cc b/cc/test/test_gpu_memory_buffer_manager.cc
index 8887feb9c2fc6d663997beb1d6f8ec6a19ba6742..a3cd357041b641d324e1721b8c9d98b4876deaaa 100644
--- a/cc/test/test_gpu_memory_buffer_manager.cc
+++ b/cc/test/test_gpu_memory_buffer_manager.cc
@@ -18,6 +18,7 @@ size_t NumberOfPlanesForGpuMemoryBufferFormat(
     case gfx::GpuMemoryBuffer::Format::DXT1:
     case gfx::GpuMemoryBuffer::Format::DXT5:
     case gfx::GpuMemoryBuffer::Format::ETC1:
+    case gfx::GpuMemoryBuffer::Format::R_8:
     case gfx::GpuMemoryBuffer::Format::RGBA_8888:
     case gfx::GpuMemoryBuffer::Format::RGBX_8888:
     case gfx::GpuMemoryBuffer::Format::BGRA_8888:
@@ -36,6 +37,7 @@ size_t SubsamplingFactor(gfx::GpuMemoryBuffer::Format format, int plane) {
     case gfx::GpuMemoryBuffer::DXT1:
     case gfx::GpuMemoryBuffer::DXT5:
     case gfx::GpuMemoryBuffer::ETC1:
+    case gfx::GpuMemoryBuffer::R_8:
     case gfx::GpuMemoryBuffer::RGBA_8888:
     case gfx::GpuMemoryBuffer::RGBX_8888:
     case gfx::GpuMemoryBuffer::BGRA_8888:
@@ -64,6 +66,8 @@ size_t StrideInBytes(size_t width,
       DCHECK_EQ(plane, 0);
       DCHECK_EQ(width % 2, 0U);
       return width / 2;
+    case gfx::GpuMemoryBuffer::R_8:
+      return (width + 3) & ~0x3;
     case gfx::GpuMemoryBuffer::RGBA_8888:
     case gfx::GpuMemoryBuffer::RGBX_8888:
     case gfx::GpuMemoryBuffer::BGRA_8888: