add note about security and new subclasses

src/ports/SkGlobalInitialization_default.cpp

Index: src/ports/SkGlobalInitialization_default.cpp
diff --git a/src/ports/SkGlobalInitialization_default.cpp b/src/ports/SkGlobalInitialization_default.cpp
index a2b91b4a933537ce23f4f1d69dd4ff1d39af2a22..8b27c49a6ef327d634f1066c55f67c2c1bf28ef5 100644
--- a/src/ports/SkGlobalInitialization_default.cpp
+++ b/src/ports/SkGlobalInitialization_default.cpp
@@ -46,6 +46,15 @@
 #include "SkTileImageFilter.h"
 #include "SkXfermodeImageFilter.h"
 
+// Security note:
+//
+// As new subclasses are added here, they should be reviewed by chrome security before they
+// support deserializing cross-process: chrome-security@google.com. SampleFilterFuzz.cpp should
+// also be amended to exercise the new subclass.
+//
+// See SkReadBuffer::isCrossProcess() and SkPicture::PictureIOSecurityPrecautionsEnabled()
+//
+
 /*
  *  None of these are strictly "required" for Skia to operate.
  *