Add Protobuf support for cc/playback skia usage

cc/proto/skregion.proto

Index: cc/proto/skregion.proto
diff --git a/cc/proto/rectf.proto b/cc/proto/skregion.proto
similarity index 59%
copy from cc/proto/rectf.proto
copy to cc/proto/skregion.proto
index 5bd56f1cb9f2d09c42146476d6b81165fa5da160..1f6b337e9b39c5e926b1ff497263b46687c0b760 100644
--- a/cc/proto/rectf.proto
+++ b/cc/proto/skregion.proto
@@ -4,14 +4,17 @@
 
 syntax = "proto2";
 
-import "pointf.proto";
-import "sizef.proto";
-
 option optimize_for = LITE_RUNTIME;
 
 package cc.proto;
 
-message RectF {
-  optional cc.proto.PointF origin = 1;
-  optional cc.proto.SizeF size = 2;
-}
+message SkRegion {
+  enum Op {
+    Op_Difference = 0;
+    Op_Intersect = 1;
+    Op_Union = 2;
+    Op_XOR = 3;
+    Op_ReverseDifference = 4;
+    Op_Replace = 5;
+  }
+}