Add a SystemApi to control display saturation.

Allows an app with the appropriate permission to reduce
(make more gray) the saturation of colors on the display.

Test: manual
Bug: 77189882
Change-Id: I2b7b065d07bd2ca24730b2e8c52d161c22b307ab
diff --git a/core/java/android/hardware/display/DisplayManagerGlobal.java b/core/java/android/hardware/display/DisplayManagerGlobal.java
index 1f67a6b..2d0ef2f 100644
--- a/core/java/android/hardware/display/DisplayManagerGlobal.java
+++ b/core/java/android/hardware/display/DisplayManagerGlobal.java
@@ -384,6 +384,17 @@
         }
     }
 
+    /**
+     * Set the level of color saturation to apply to the display.
+     */
+    public void setSaturationLevel(float level) {
+        try {
+            mDm.setSaturationLevel(level);
+        } catch (RemoteException ex) {
+            throw ex.rethrowFromSystemServer();
+        }
+    }
+
     public VirtualDisplay createVirtualDisplay(Context context, MediaProjection projection,
             String name, int width, int height, int densityDpi, Surface surface, int flags,
             VirtualDisplay.Callback callback, Handler handler, String uniqueId) {