Clearify code around hasImage and hasPath

* hasImage is not needed. I determined that a nullptr is never possible.
* hasPath is renamed to decideShouldDrawFromPath. Comment the code to
  explain the symmetry of calls between Renderer and GPU.

Change-Id: I4bc74fa49cf388d43aeb3ff201053332145fee59
Reviewed-on: https://skia-review.googlesource.com/c/190678
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Khushal Sagar <khushalsagar@google.com>
7 files changed