DefaultProcessorAttribute に渡すプロセッサ名と、実際に選ばれるコンテンツ・プロセッサ名の一覧。
  EffectProcessor        → Effect - XNA Framework
  MaterialProcessor → Material - XNA Framework
  ModelProcessor → Model - XNA Framework
  ModelTextureProcessor → Texture (Model, DXT, mipmapped)
   - XNA Framework
  PassThroughProcessor → No Processing Required
  SpriteTextureProcessor → Texture (Sprite, 32bpp) - XNA Framework
  TextureProcessor → Texture (mipmapped) - XNA Framework