Roll skia to fix bots

The version of Skia we are using does not pass the new DEPS file
validation. This CL syncs to the latest Skia in order to fix the DEPS
issue.

TBR=tsepez@chromium.org
Bug: chromium:727394, chromium:570091
Change-Id: Id475ff5c98e1bc75ee76fdfc44df972ef1d53cc8
Reviewed-on: https://pdfium-review.googlesource.com/6076
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/DEPS b/DEPS
index dc3835a..169dac8 100644
--- a/DEPS
+++ b/DEPS
@@ -20,7 +20,7 @@
   'jpeg_turbo_revision': '7260e4d8b8e1e40b17f03fafdf1cd83296900f76',
   'markupsafe_revision': '8f45f5cfa0009d2a70589bcda0349b8cb2b72783',
   'pdfium_tests_revision': '5379e0a6580443318c8192cdfc78a76e880ca3f6',
-  'skia_revision': '90e3cd78991ef337dbd0023efb30ece864694308',
+  'skia_revision': 'bb581ce30f55360fd3a12e7f5aa1fe324b16d085',
   'tools_memory_revision': '427f10475e1a8d72424c29d00bf689122b738e5d',
   'trace_event_revision': '06294c8a4a6f744ef284cd63cfe54dbf61eea290',
   'v8_revision': '07b2253a044bffa43697c6a43aaccb68c7e82af4',