fix fuzzer build & signedness of a test comparison (for chrome)

Change-Id: I27f831e0a5a79a5a4761698a586299f18f5311a1
diff --git a/test/end_to_end_shared_memory_fuzzer.cc b/test/end_to_end_shared_memory_fuzzer.cc
index 3c32409..c390340 100644
--- a/test/end_to_end_shared_memory_fuzzer.cc
+++ b/test/end_to_end_shared_memory_fuzzer.cc
@@ -99,6 +99,7 @@
   void StopDataSource(DataSourceInstanceID) override {}
   void OnTracingSetup() override {}
   void Flush(FlushRequestID, const DataSourceInstanceID*, size_t) override {}
+  void ClearIncrementalState(const DataSourceInstanceID*, size_t) {}
 
  private:
   const std::string name_;