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

This reverts commit 1d6281d4bb47510754f2c821482ee120c91bd438.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> 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>

TBR=mtklein@google.com,brianosman@google.com

Change-Id: I79bb37236a0a51097e1ab3bea9b5895adc974045
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/155561
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed