SF: Save proto traces to a specific path

Test: presubmit
Bug: 200284593

Change-Id: I6987329cc32b2ca13e76e957a5ae6b17bbed6e83
diff --git a/services/surfaceflinger/Tracing/TransactionTracing.h b/services/surfaceflinger/Tracing/TransactionTracing.h
index c20f22a..95256c4 100644
--- a/services/surfaceflinger/Tracing/TransactionTracing.h
+++ b/services/surfaceflinger/Tracing/TransactionTracing.h
@@ -55,7 +55,7 @@
 
     void addQueuedTransaction(const TransactionState&);
     void addCommittedTransactions(std::vector<TransactionState>& transactions, int64_t vsyncId);
-    status_t writeToFile();
+    status_t writeToFile(std::string filename = FILE_NAME);
     void setBufferSize(size_t bufferSizeInBytes);
     void onLayerAdded(BBinder* layerHandle, int layerId, const std::string& name, uint32_t flags,
                       int parentId);