Remove implicit conversions from scoped_refptr to T* in ppapi/

ppapi/proxy/ppb_graphics_3d_proxy.cc

Index: ppapi/proxy/ppb_graphics_3d_proxy.cc
diff --git a/ppapi/proxy/ppb_graphics_3d_proxy.cc b/ppapi/proxy/ppb_graphics_3d_proxy.cc
index 0d383c939603bb6339211afbf05beb8358215aa2..4bb7b8dc4a21c53c9297e667e76807186e8546d8 100644
--- a/ppapi/proxy/ppb_graphics_3d_proxy.cc
+++ b/ppapi/proxy/ppb_graphics_3d_proxy.cc
@@ -290,7 +290,7 @@ void PPB_Graphics3D_Proxy::OnMsgCreateTransferBuffer(
   if (enter.succeeded()) {
     scoped_refptr<gpu::Buffer> buffer =
         enter.object()->CreateTransferBuffer(size, id);
-    if (!buffer)
+    if (!buffer.get())
       return;
     gpu::SharedMemoryBufferBacking* backing =
         static_cast<gpu::SharedMemoryBufferBacking*>(buffer->backing());