Added the framework for having canvas/recorder/picture record depth_set's.

include/private/SkRecords.h

Index: include/private/SkRecords.h
diff --git a/include/private/SkRecords.h b/include/private/SkRecords.h
index d6ef12fe6c36491229f83253d921f8f914a52ffc..497c3c72c03edca87fbda8f375574fa80b51c0e5 100644
--- a/include/private/SkRecords.h
+++ b/include/private/SkRecords.h
@@ -47,6 +47,7 @@ namespace SkRecords {
     M(Save)                                                         \
     M(SaveLayer)                                                    \
     M(SetMatrix)                                                    \
+    M(SetZ)                                                         \
     M(Concat)                                                       \
     M(ClipPath)                                                     \
     M(ClipRRect)                                                    \
@@ -217,6 +218,8 @@ RECORD(SetMatrix, 0,
 RECORD(Concat, 0,
         TypedMatrix matrix);
 
+RECORD(SetZ, 0, uint32_t z);
+
 struct RegionOpAndAA {
     RegionOpAndAA() {}
     RegionOpAndAA(SkRegion::Op op, bool aa) : op(op), aa(aa) {}