update skia

Update Skia to the last revision that passed the Chrome DEPS roll.
This will help green the Skia tree so that future changes to Skia
that break PDFium can be detected.

R=rmistry@google.com,dsinclair@chromium.org

Review-Url: https://codereview.chromium.org/2042403004
diff --git a/DEPS b/DEPS
index f902521..27e7a28 100644
--- a/DEPS
+++ b/DEPS
@@ -13,7 +13,7 @@
   'gtest_revision': '8245545b6dc9c4703e6496d1efd19e975ad2b038',
   'icu_revision': 'c291cde264469b20ca969ce8832088acb21e0c48',
   'pdfium_tests_revision': '6c769320872e6ca82da4adaec1a497237f71b543',
-  'skia_revision': '6f47dbaff54a7705ef3e98f1f65c765e56fd9bd0',
+  'skia_revision': '7942f22c607caf826a6a609b89338a569d0a30e7',
   'tools_memory_revision': '427f10475e1a8d72424c29d00bf689122b738e5d',
   'trace_event_revision': 'd83d44b13d07c2fd0a40101a7deef9b93b841732',
   'v8_revision': '055bfa771a7bd763305d3bafd43e39459abc95a4',