fix --show-composited-layer-borders on Mac

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
index 5ec2a318d4972870ffecb258c00ca20abb8bc58a..809314071ab6d55032e4d44e23143316170a7fa6 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
@@ -2604,5 +2604,18 @@ error::Error GLES2DecoderPassthroughImpl::HandleCompressedTexSubImage3D(
       format, image_size, data);
 }
 
+error::Error GLES2DecoderPassthroughImpl::HandleLineWidth(
+    uint32_t immediate_data_size,
+    const volatile void* cmd_data) {
+  const volatile gles2::cmds::LineWidth& c =
+      *static_cast<const volatile gles2::cmds::LineWidth*>(cmd_data);
+  GLfloat width = static_cast<GLfloat>(c.width);
+  error::Error error = DoLineWidth(width);
+  if (error != error::kNoError) {
+    return error;
+  }
+  return error::kNoError;
+}
+
 }  // namespace gles2
 }  // namespace gpu