Reland "implement SkPixmap::getPixel() with this->readPixels()."

This is a reland of 0944ae8afbafaae30eacffc73c5afbf4c062210c

Original change's description:
> implement SkPixmap::getPixel() with this->readPixels().
> 
> Yet another big old switch statement I don't want to maintain.
> 
> Once again, I think this at least makes it explicit that we're
> returning an SkColor in the colorspace of the pixmap.
> 
> Change-Id: I34aa7312c0a1670910586fc5a4b1951275e73e2e
> Reviewed-on: https://skia-review.googlesource.com/154864
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

Change-Id: I07b0b11922a393072961edc7771d7a972ca1fd13
Reviewed-on: https://skia-review.googlesource.com/155166
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed