Roll Skia from 650913eacd01 to 15a2577b12c1 (1 revision) (flutter/engine#48036)

https://skia.googlesource.com/skia.git/+log/650913eacd01..15a2577b12c1

2023-11-14 kjlubick@google.com Add buffet rule for png encoding and fontconfig SkFontMgr

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC brianosman@google.com,jonahwilliams@google.com,nicolettep@google.com,rmistry@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Skia: https://bugs.chromium.org/p/skia/issues/entry
To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

DEPS

@@ -18,7 +18,7 @@ vars = {
   'llvm_git': 'https://llvm.googlesource.com',
   # OCMock is for testing only so there is no google clone
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
-  'skia_revision': '650913eacd01eee5ec0658083f67739763372e25',
+  'skia_revision': '15a2577b12c1d873595561801a68e073dcc614fb',
 
   # WARNING: DO NOT EDIT canvaskit_cipd_instance MANUALLY
   # See `lib/web_ui/README.md` for how to roll CanvasKit to a new version.