Remove legacy layer path in screenshot pathway

Legacy path to get layer snapshots is no longer used
and the flag can be removed to clean up the code.
Also renames layer snapshot function variable for better
clarity that the function is not immediately called wherever
declared.

Bug: b/330785038
Test: presubmit
Test: atest SurfaceFlinger_test
Change-Id: I12498f2560de07d69fff93eda901f6b7c072fce6
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 1783e17..7889096 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -487,7 +487,7 @@
 
     auto renderScreenImpl(const sp<DisplayDevice> display,
                           std::unique_ptr<const RenderArea> renderArea,
-                          SurfaceFlinger::GetLayerSnapshotsFunction traverseLayers,
+                          SurfaceFlinger::GetLayerSnapshotsFunction getLayerSnapshotsFn,
                           const std::shared_ptr<renderengine::ExternalTexture>& buffer,
                           bool regionSampling) {
         Mutex::Autolock lock(mFlinger->mStateLock);
@@ -495,7 +495,7 @@
 
         ScreenCaptureResults captureResults;
         SurfaceFlinger::OutputCompositionState state = display->getCompositionDisplay()->getState();
-        auto layers = mFlinger->getLayerSnapshotsFromMainThread(traverseLayers);
+        auto layers = mFlinger->getLayerSnapshotsFromMainThread(getLayerSnapshotsFn);
 
         return mFlinger->renderScreenImpl(std::move(renderArea), buffer, regionSampling,
                                           false /* grayscale */, false /* isProtected */,
@@ -505,8 +505,7 @@
     auto traverseLayersInLayerStack(ui::LayerStack layerStack, int32_t uid,
                                     std::unordered_set<uint32_t> excludeLayerIds,
                                     const LayerVector::Visitor& visitor) {
-        return mFlinger->SurfaceFlinger::traverseLayersInLayerStack(layerStack, uid,
-                                                                    excludeLayerIds, visitor);
+        return mFlinger->traverseLayersInLayerStack(layerStack, uid, excludeLayerIds, visitor);
     }
 
     auto getDisplayNativePrimaries(const sp<IBinder>& displayToken,