Provide classes that logically make up a transaction with == and !=.

Primarily this change is intended to support writing test assertions.
As a side effect, make some improvements to encapsulation of members.

Flag: EXEMPT refactor
Bug: 385156191
Test: presubmit

Change-Id: I51352c78ccfcb0fc6bff655593d7d31771516668
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 6af0f59..081bb22 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -288,7 +288,7 @@
                                         bool leaveState);
 
     inline bool hasTrustedPresentationListener() {
-        return mTrustedPresentationListener.callbackInterface != nullptr;
+        return mTrustedPresentationListener.getCallback() != nullptr;
     }
 
     // Sets the masked bits.