Expose transaction id

We will need to dump the transaction id in transition traces to be able to reliably associated the start and end of a transition to the states in the SF trace.

Bug: 230462538
Test: N/A
Change-Id: I31d997c4e2b48945bb7181ed82e197f5980ef02c
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 47d801a..9358e29 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -897,6 +897,10 @@
     mApplyToken = nullptr;
 }
 
+uint64_t SurfaceComposerClient::Transaction::getId() {
+    return mId;
+}
+
 void SurfaceComposerClient::doUncacheBufferTransaction(uint64_t cacheId) {
     sp<ISurfaceComposer> sf(ComposerService::getComposerService());