Don't delete objects twice...

        SkiaShader* shaderCopy = mShaderMap.valueFor(shader);

        // TODO: We also need to handle generation ID changes in compose shaders

        if (!shaderCopy || shaderCopy->getGenerationId() != shader->getGenerationId()) {

        if (shaderCopy == NULL || shaderCopy->getGenerationId() != shader->getGenerationId()) {

            shaderCopy = shader->copy();

            mShaderMap.add(shader, shaderCopy);

            mShaders.add(shader);

            mShaders.add(shaderCopy);

        }

        addInt((int) shaderCopy);