[Sync] Initial support for encrypting any datatype (no UI hookup yet).

chrome/browser/sync/protocol/sync.proto

Index: chrome/browser/sync/protocol/sync.proto
diff --git a/chrome/browser/sync/protocol/sync.proto b/chrome/browser/sync/protocol/sync.proto
index 1ada9519bdd9664999e41229788c4af2c75c8d26..2f4f87c92da620736d459e420e31c193e572df50 100644
--- a/chrome/browser/sync/protocol/sync.proto
+++ b/chrome/browser/sync/protocol/sync.proto
@@ -11,6 +11,8 @@ option retain_unknown_fields = true;
 
 package sync_pb;
 
+import "encryption.proto";
+
 // Used for inspecting how long we spent performing operations in different
 // backends. All times must be in millis.
 message ProfilingData {
@@ -23,6 +25,8 @@ message ProfilingData {
 }
 
 message EntitySpecifics {
+  optional EncryptedData encrypted = 1;
+
   // To add new datatype-specific fields to the protocol, extend
   // EntitySpecifics.  First, pick a non-colliding tag number by
   // picking a revision number of one of your past commits