SF: Add a flag for the connected-display feature

Bug: 299486625
Test: adb shell dumpsys SurfaceFlinger  -- check for
"ConnectedDisplayFlagValue"

Change-Id: I4526091ca938ef378877edf63b499a3c8c8a39d9
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index f752584..59b1172 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1451,7 +1451,9 @@
     void sfdo_scheduleComposite();
     void sfdo_scheduleCommit();
 
+    // Trunk-Stable flags
     bool mMiscFlagValue;
+    bool mConnectedDisplayFlagValue;
 };
 
 class SurfaceComposerAIDL : public gui::BnSurfaceComposer {