Added a Bounds() method to Texture

canvas/texture.go

@@ -11,6 +11,9 @@ type Texture interface {
 	// internal data. Becaue of this, closing a clipped section will close
 	// the original texture as well.
 	Clip (image.Rectangle) Texture
+
+	// Bounds returns the size of this texture.
+	Bounds () image.Rectangle
 }
 
 type protectedTexture struct {