AU: Don't send no-op operations in the delta payload.

delta_diff_generator.h

Index: delta_diff_generator.h
diff --git a/delta_diff_generator.h b/delta_diff_generator.h
index de3be0da0494e89c1fd46ecc678a03e86d516b1f..9fbe0a55cc1e7314c6b67276678af5ccf2bc6139 100644
--- a/delta_diff_generator.h
+++ b/delta_diff_generator.h
@@ -211,6 +211,10 @@ class DeltaDiffGenerator {
       std::vector<DeltaArchiveManifest_InstallOperation>* kernel_ops,
       std::vector<Vertex::Index>* final_order);
 
+  // Returns true if |op| is a no-op operation that doesn't do any useful work
+  // (e.g., a move operation that copies blocks onto themselves).
+  static bool IsNoopOperation(const DeltaArchiveManifest_InstallOperation& op);
+
  private:
   // This should never be constructed
   DISALLOW_IMPLICIT_CONSTRUCTORS(DeltaDiffGenerator);