Query the new DisplayCapability for DISPLAY_DECORATION

This allows clients (i.e. SystemUi) to know whether to use
Composition.DISPLAY_DECORATION.

Bug: 193170859
Test: manual
Test: TODO (b/212697197)

Change-Id: I0d3e93bb04937f81e95ef77d196b861621bbdc8d
diff --git a/services/surfaceflinger/DisplayHardware/Hal.h b/services/surfaceflinger/DisplayHardware/Hal.h
index e33dc0f..ee06e03 100644
--- a/services/surfaceflinger/DisplayHardware/Hal.h
+++ b/services/surfaceflinger/DisplayHardware/Hal.h
@@ -136,6 +136,8 @@
             return "AutoLowLatencyMode";
         case aidl::android::hardware::graphics::composer3::DisplayCapability::SUSPEND:
             return "Suspend";
+        case aidl::android::hardware::graphics::composer3::DisplayCapability::DISPLAY_DECORATION:
+            return "DisplayDecoration";
         default:
             return "Unknown";
     }