Update MultiDisplay_test for duplicate layerstacks

Duplicate layerstacks are no longer permitted, but existing
MultiDisplay tests do not catch these cases since the tests
do not go through the SF composite path where the duplicates
are rejected. Mirroring logic between physical and virtual
displays is no longer applicable, and an exisiting test already
captures this mirroring logic without duplicate layerstacks.

Bug: b/370358572
Test: atest MultiDisplayTest
Flag: EXEMPT, update test
Change-Id: I301c049740597865e72ea7450b692e5278dca24d

Author: Melody Hsu

services/surfaceflinger/tests/MultiDisplay_test.cpp

@@ -125,39 +125,14 @@ TEST_F(MultiDisplayTest, RenderLayerInVirtualDisplay) {
 }
 
 TEST_F(MultiDisplayTest, RenderLayerInMirroredVirtualDisplay) {
-    // Create a display and set its layer stack to the main display's layer stack so
-    // the contents of the main display are mirrored on to the virtual display.
-
-    // Assumption here is that the new mirrored display has the same layer stack rect as the
-    // primary display that it is mirroring.
-    createDisplay(mMainDisplayState.layerStackSpaceRect, ui::DEFAULT_LAYER_STACK);
-    createColorLayer(ui::DEFAULT_LAYER_STACK);
-
-    sp<SurfaceControl> mirrorSc =
-            SurfaceComposerClient::getDefault()->mirrorDisplay(mMainDisplayId);
-
-    asTransaction([&](Transaction& t) { t.setPosition(mColorLayer, 10, 10); });
-
-    // Verify color layer renders correctly on main display and it is mirrored on the
-    // virtual display.
-    std::unique_ptr<ScreenCapture> sc;
-    ScreenCapture::captureScreen(&sc, mMainDisplay);
-    sc->expectColor(Rect(10, 10, 40, 50), mExpectedColor);
-    sc->expectColor(Rect(0, 0, 9, 9), {0, 0, 0, 255});
-
-    ScreenCapture::captureScreen(&sc, mVirtualDisplay);
-    sc->expectColor(Rect(10, 10, 40, 50), mExpectedColor);
-    sc->expectColor(Rect(0, 0, 9, 9), {0, 0, 0, 255});
-}
-
-TEST_F(MultiDisplayTest, RenderLayerWithPromisedFenceInMirroredVirtualDisplay) {
     // Create a display and use a unique layerstack ID for mirrorDisplay() so
     // the contents of the main display are mirrored on to the virtual display.
 
     // A unique layerstack ID must be used because sharing the same layerFE
     // with more than one display is unsupported. A unique layerstack ensures
-    // that a different layerFE is used between displays.
-    constexpr ui::LayerStack layerStack{77687666}; // ASCII for MDLB (MultiDisplayLayerBounds)
+    // that a different layerFE is used between displays. Each layerFE has a
+    // promised fence that is each fulfilled.
+    constexpr ui::LayerStack layerStack{776884}; // ASCII for MDT (MultiDisplayTest)
     createDisplay(mMainDisplayState.layerStackSpaceRect, layerStack);
     createColorLayer(ui::DEFAULT_LAYER_STACK);