Revert of Remove public_headers.gypi, unneeded by Skia. (https://codereview.chromium...

Revert of Remove public_headers.gypi, unneeded by Skia. (https://codereview.chromium.org/381633003/)

Reason for revert:
Breaking canary: http://108.170.220.120:10117/builders/Canary-Chrome-Ubuntu13.10-Ninja-x86_64-ToT/builds/1207/steps/Update/logs/stdio

Original issue's description:
> Remove public_headers.gypi, unneeded by Skia.
>
> This file not needed by Skia, and is almost always out of date.
> We recommend generating this inside Android WebView, where it is
> used. Generating it is relatively straightforward; here is one way:
> https://codereview.chromium.org/198063002/diff/110001/platform_tools/android/gyp_gen/gen_public_headers.py
>
> BUG=skia:2350
>
> Committed: https://skia.googlesource.com/skia/+/a3fce46f7c85eb3eb5c5373c1eaa0336d9756252

R=robertphillips@google.com
TBR=robertphillips@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2350

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/382153007