CE: Introduce CompositionEngine::dump()

Allow any CompositionEngine state to be dumped as part of
SurfaceFlinger's dump.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Test: go/wm-smoke
Bug: 121291683
Change-Id: I4b87ff912c767538f2d371c342f782e92c4e74e9
diff --git a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
index 295c289..be8646c 100644
--- a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
@@ -130,6 +130,10 @@
     mNeedsAnotherUpdate = needsAnotherUpdate;
 }
 
+void CompositionEngine::dump(std::string&) const {
+    // The base class has no state to dump, but derived classes might.
+}
+
 void CompositionEngine::setNeedsAnotherUpdateForTest(bool value) {
     mNeedsAnotherUpdate = value;
 }