Clarify cutoff priorities

            // This can happen if a BitmapShader is used on multiple canvas', such as a

            // software + hardware canvas, which is otherwise valid as SkShader is "immutable"

            std::lock_guard _lock(mUniformGuard);

            const float Wunclamped = (sk_float_log(targetHdrSdrRatio) -

            // Compute the weight parameter that will be used to blend between the images.

            float W = 0.f;

            if (targetHdrSdrRatio > mGainmapInfo.fDisplayRatioSdr) {

                if (targetHdrSdrRatio < mGainmapInfo.fDisplayRatioHdr) {

                    W = (sk_float_log(targetHdrSdrRatio) -

                         sk_float_log(mGainmapInfo.fDisplayRatioSdr)) /

                        (sk_float_log(mGainmapInfo.fDisplayRatioHdr) -

                         sk_float_log(mGainmapInfo.fDisplayRatioSdr));

            const float W = std::max(std::min(Wunclamped, 1.f), 0.f);

                } else {

                    W = 1.f;

                }

            }

            mBuilder.uniform("W") = W;

            uniforms = mBuilder.uniforms();

        }