Write XOR ops for bsdiff and puffdiff

Test: th
Bug: 177104308

Change-Id: I10f79f1a2de910e5ba57a72a5dba5901c9348d77
diff --git a/common/mock_dynamic_partition_control.h b/common/mock_dynamic_partition_control.h
index bfd1b0c..c6b0b2d 100644
--- a/common/mock_dynamic_partition_control.h
+++ b/common/mock_dynamic_partition_control.h
@@ -50,12 +50,10 @@
               (const std::string&, const InstallOperation&, InstallOperation*),
               (override));
 
-  std::unique_ptr<android::snapshot::ISnapshotWriter> OpenCowWriter(
-      const std::string& unsuffixed_partition_name,
-      const std::optional<std::string>&,
-      bool is_append = false) override {
-    return nullptr;
-  }
+  MOCK_METHOD(std::unique_ptr<android::snapshot::ISnapshotWriter>,
+              OpenCowWriter,
+              (const std::string&, const std::optional<std::string>&, bool),
+              (override));
 
   MOCK_METHOD(
       bool,