Split picture version into min & max supported versions

include/core/SkPicture.h

Index: include/core/SkPicture.h
===================================================================
--- include/core/SkPicture.h	(revision 13567)
+++ include/core/SkPicture.h	(working copy)
@@ -242,8 +242,11 @@
 
     // Note: If the picture version needs to be increased then please follow the
     // steps to generate new SKPs in (only accessible to Googlers): http://goo.gl/qATVcw
-    static const uint32_t PICTURE_VERSION = 20;
 
+    // Only SKPs within the min/current picture version range (inclusive) can be read.
+    static const uint32_t MIN_PICTURE_VERSION = 20;

[mtklein, 2014/02/24 19:58:38]

Just curious: we believe this is actually 19?

[robertphillips, 2014/02/24 20:05:48]

I suspect it is but I was going to consult Alexis about that after this CL.

[robertphillips, 2014/02/24 20:13:19]

Chatted with Alexis and he agreed 19 should be okay. Done.

+    static const uint32_t CURRENT_PICTURE_VERSION = 20;
+
     // fPlayback, fRecord, fWidth & fHeight are protected to allow derived classes to
     // install their own SkPicturePlayback-derived players,SkPictureRecord-derived
     // recorders and set the picture size