Add a TestApi to DM to get the last requested MPP

This CL exposes DisplayManager.getRequestedMinimalPostProcessing
for testing purposes. The call is propagated to
LogicalDisplay.getRequestedMinimalPostProcessingLocked().

Bug: 139369866

Test: m, flash, atest
CtsWindowManagerDeviceTestCases:MinimalPostProcessingTests

Change-Id: I7736d6e7a5c97d663111d10efa66d6d38a7e70bd
diff --git a/services/core/java/com/android/server/display/DisplayManagerService.java b/services/core/java/com/android/server/display/DisplayManagerService.java
index e39d6d5..58e519d 100644
--- a/services/core/java/com/android/server/display/DisplayManagerService.java
+++ b/services/core/java/com/android/server/display/DisplayManagerService.java
@@ -2244,6 +2244,13 @@
         }
 
         @Override // Binder call
+        public boolean isMinimalPostProcessingRequested(int displayId) {
+            synchronized (mSyncRoot) {
+                return mLogicalDisplays.get(displayId).getRequestedMinimalPostProcessingLocked();
+            }
+        }
+
+        @Override // Binder call
         public void setTemporaryBrightness(int brightness) {
             mContext.enforceCallingOrSelfPermission(
                     Manifest.permission.CONTROL_DISPLAY_BRIGHTNESS,