SF: Remove unused SurfaceFlinger::getLayerSortedByZForHwcDisplay

There were no callers, and it relied on CompositionEngine state being
made internal to the new code.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Bug: 121291683
Change-Id: I896ccc65c13acf3d9ea87c65da388b06f35ac175
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 4a4db4c..36e6956 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -4972,19 +4972,6 @@
     result.append("\n");
 }
 
-const Vector<sp<Layer>>& SurfaceFlinger::getLayerSortedByZForHwcDisplay(DisplayId displayId) {
-    // Note: mStateLock is held here
-    for (const auto& [token, display] : mDisplays) {
-        if (display->getId() == displayId) {
-            return getDisplayDeviceLocked(token)->getVisibleLayersSortedByZ();
-        }
-    }
-
-    ALOGE("%s: Invalid display %s", __FUNCTION__, to_string(displayId).c_str());
-    static const Vector<sp<Layer>> empty;
-    return empty;
-}
-
 void SurfaceFlinger::updateColorMatrixLocked() {
     mat4 colorMatrix;
     if (mGlobalSaturationFactor != 1.0f) {
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index f953234..f5ff01e 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -304,10 +304,6 @@
     // TODO: this should be made accessible only to MessageQueue
     void onMessageReceived(int32_t what);
 
-    // for debugging only
-    // TODO: this should be made accessible only to HWComposer
-    const Vector<sp<Layer>>& getLayerSortedByZForHwcDisplay(DisplayId displayId);
-
     renderengine::RenderEngine& getRenderEngine() const;
 
     bool authenticateSurfaceTextureLocked(