[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 6af021bbd0d71a383432ca751fa06fc279b66ac5..a87b0b35c837599d5db809ac98e55fa06499efa8 100644
--- a/chrome/browser/sync/protocol/sync.proto
+++ b/chrome/browser/sync/protocol/sync.proto
@@ -14,6 +14,8 @@ 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 {
@@ -26,6 +28,13 @@ message ProfilingData {
 }
 
 message EntitySpecifics {
+  // If a datatype is encrypted, this field will contain the encrypted
+  // original EntitySpecifics. The extension for the datatype will continue
+  // to exist, but contain only the default values.
+  // Note that currently passwords employ their own legacy encryption scheme and
+  // do not use this field.
+  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