sync: Move unique_client_tag hashing code

sync/internal_api/public/base_node.h

Index: sync/internal_api/public/base_node.h
diff --git a/sync/internal_api/public/base_node.h b/sync/internal_api/public/base_node.h
index 8afbeaae0bb29dd8b0c8c364828b5c0b89039e2e..b3946fb17c6af85c781bccdf711f41a2fcea73c2 100644
--- a/sync/internal_api/public/base_node.h
+++ b/sync/internal_api/public/base_node.h
@@ -200,11 +200,6 @@ class SYNC_EXPORT BaseNode {
  protected:
   BaseNode();
   virtual ~BaseNode();
-  // The server has a size limit on client tags, so we generate a fixed length
-  // hash locally. This also ensures that ModelTypes have unique namespaces.
-  static std::string GenerateSyncableHash(
-      ModelType model_type,
-      const std::string& client_tag);
 
   // Determines whether part of the entry is encrypted, and if so attempts to
   // decrypt it. Unless decryption is necessary and fails, this will always