Revert of Pass initial size and GPU preference via context attributes

components/display_compositor/yuv_readback_unittest.cc

Index: components/display_compositor/yuv_readback_unittest.cc
diff --git a/components/display_compositor/yuv_readback_unittest.cc b/components/display_compositor/yuv_readback_unittest.cc
index 91f1d2fbdad55f3615ece29ad17f3cd4987d69de..b336137bbdbda77e1e2df5b118ddfb04a27af24c 100644
--- a/components/display_compositor/yuv_readback_unittest.cc
+++ b/components/display_compositor/yuv_readback_unittest.cc
@@ -43,8 +43,9 @@
         nullptr,                     /* surface */
         true,                        /* offscreen */
         gfx::kNullAcceleratedWidget, /* window */
+        gfx::Size(1, 1),             /* size */
         nullptr,                     /* share_context */
-        attributes, gpu::SharedMemoryLimits(),
+        attributes, gl::PreferDiscreteGpu, gpu::SharedMemoryLimits(),
         nullptr, /* gpu_memory_buffer_manager */
         nullptr /* image_factory */));
     gl_ = context_->GetImplementation();