Undeprecate animation background color

Now that we support showing a background color behind animations again
to makes sense to undeprecate the background color animation API so the
background color can be set during in the animation's definition.

Test: atest CtsWindowManagerDeviceTestCases:ActivityTransitionTests
Change-Id: I1bd1468f7ae4ee41f5d2d25947852c78b93bc6ee

core/api/current.txt

@@ -52206,7 +52206,7 @@ package android.view.animation {
     method protected android.view.animation.Animation clone() throws java.lang.CloneNotSupportedException;
     method public long computeDurationHint();
     method protected void ensureInterpolator();
-    method @Deprecated @ColorInt public int getBackgroundColor();
+    method @ColorInt public int getBackgroundColor();
     method @Deprecated public boolean getDetachWallpaper();
     method public long getDuration();
     method public boolean getFillAfter();
@@ -52231,7 +52231,7 @@ package android.view.animation {
     method public void restrictDuration(long);
     method public void scaleCurrentDuration(float);
     method public void setAnimationListener(android.view.animation.Animation.AnimationListener);
-    method @Deprecated public void setBackgroundColor(@ColorInt int);
+    method public void setBackgroundColor(@ColorInt int);
     method @Deprecated public void setDetachWallpaper(boolean);
     method public void setDuration(long);
     method public void setFillAfter(boolean);

core/java/android/view/animation/Animation.java

@@ -646,11 +646,9 @@ public abstract class Animation implements Cloneable {
      * @param bg The background color.  If 0, no background.  Currently must
      * be black, with any desired alpha level.
      *
-     * @deprecated None of window animations are running with background color.
      */
-    @Deprecated
     public void setBackgroundColor(@ColorInt int bg) {
-        // The background color is not needed any more, do nothing.
+        mBackgroundColor = bg;
     }
 
     /**
@@ -824,13 +822,10 @@ public abstract class Animation implements Cloneable {
 
     /**
      * Returns the background color behind the animation.
-     *
-     * @deprecated None of window animations are running with background color.
      */
-    @Deprecated
     @ColorInt
     public int getBackgroundColor() {
-        return 0;
+        return mBackgroundColor;
     }
 
     /**

libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultTransitionHandler.java

@@ -430,6 +430,10 @@ public class DefaultTransitionHandler implements Transitions.TransitionHandler {
                         // If available use the background color provided through AnimationOptions
                         backgroundColorForTransition =
                                 info.getAnimationOptions().getBackgroundColor();
+                    } else if (a.getBackgroundColor() != 0) {
+                        // Otherwise fallback on the background color provided through the animation
+                        // definition.
+                        backgroundColorForTransition = a.getBackgroundColor();
                     } else if (change.getBackgroundColor() != 0) {
                         // Otherwise default to the window's background color if provided through
                         // the theme as the background color for the animation - the top most window