[MD] Single refresh rate selection

Selects the single refresh rate for all the
displays.

BUG: 240743471

Test: atest libsurfaceflinger_unittest
Change-Id: Ifa1bf23bc991fe60e67dba1cb31077e42fd5396e
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 5338f4a..f5042d3 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -842,6 +842,9 @@
 
             sp<DisplayDevice> display = sp<DisplayDevice>::make(mCreationArgs);
             mFlinger.mutableDisplays().emplace_or_replace(mDisplayToken, display);
+            if (mFlinger.scheduler()) {
+                mFlinger.scheduler()->registerDisplay(display);
+            }
 
             DisplayDeviceState state;
             state.isSecure = mCreationArgs.isSecure;