Apply letterbox changes when background color changes.

Fix: 179380577
Test: atest LetterboxTest
Change-Id: Ieedbb2a30bd66ee1aa474eed9e5c9b013520a838

services/core/java/com/android/server/wm/Letterbox.java

@@ -340,7 +340,7 @@ public class Letterbox {
         }
 
         public void applySurfaceChanges(SurfaceControl.Transaction t) {
-            if (mSurfaceFrameRelative.equals(mLayoutFrameRelative)) {
+            if (!needsApplySurfaceChanges()) {
                 // Nothing changed.
                 return;
             }

services/tests/wmtests/src/com/android/server/wm/LetterboxTest.java

@@ -183,6 +183,10 @@ public class LetterboxTest {
         mColor = Color.GREEN;
 
         assertTrue(mLetterbox.needsApplySurfaceChanges());
+
+        mLetterbox.applySurfaceChanges(mTransaction);
+
+        verify(mTransaction).setColor(mSurfaces.top, new float[]{0, 1, 0});
     }
 
     @Test