Add test api getStatus/NavigationBarBackgroundView.

Introduces new test api to access the background view of status bar and
navigation bar.

Bug: 154720832
Test: atest WindowInsetsPolicyTest

Change-Id: If38d3f57edfbb2631d4c1e47ed5347a332edacfb

api/test-current.txt

@@ -4966,6 +4966,11 @@ package android.view {
     method @Nullable public static AutoCloseable startRenderingCommandsCapture(android.view.View, java.util.concurrent.Executor, java.util.concurrent.Callable<java.io.OutputStream>);
   }
 
+  public abstract class Window {
+    method @Nullable public android.view.View getNavigationBarBackgroundView();
+    method @Nullable public android.view.View getStatusBarBackgroundView();
+  }
+
   public interface WindowManager extends android.view.ViewManager {
     method public default void setShouldShowIme(int, boolean);
     method public default void setShouldShowSystemDecors(int, boolean);

core/java/android/view/Window.java

@@ -26,6 +26,7 @@ import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.StyleRes;
 import android.annotation.SystemApi;
+import android.annotation.TestApi;
 import android.app.WindowConfiguration;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.content.Context;
@@ -1794,6 +1795,24 @@ public abstract class Window {
      */
     public abstract @NonNull View getDecorView();
 
+    /**
+     * @return the status bar background view or null.
+     * @hide
+     */
+    @TestApi
+    public @Nullable View getStatusBarBackgroundView() {
+        return null;
+    }
+
+    /**
+     * @return the navigation bar background view or null.
+     * @hide
+     */
+    @TestApi
+    public @Nullable View getNavigationBarBackgroundView() {
+        return null;
+    }
+
     /**
      * Retrieve the current decor view, but only if it has already been created;
      * otherwise returns null.

core/java/com/android/internal/policy/DecorView.java

@@ -324,6 +324,14 @@ public class DecorView extends FrameLayout implements RootViewSurfaceTaker, Wind
         return mBackgroundFallback.getDrawable();
     }
 
+    @Nullable View getStatusBarBackgroundView() {
+        return mStatusColorViewState.view;
+    }
+
+    @Nullable View getNavigationBarBackgroundView() {
+        return mNavigationColorViewState.view;
+    }
+
     @Override
     public boolean gatherTransparentRegion(Region region) {
         boolean statusOpaque = gatherTransparentRegion(mStatusColorViewState, region);

core/java/com/android/internal/policy/PhoneWindow.java

@@ -38,6 +38,7 @@ import static android.view.WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE;
 import static android.view.WindowManager.LayoutParams.SOFT_INPUT_MASK_ADJUST;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.app.ActivityManager;
 import android.app.KeyguardManager;
 import android.app.SearchManager;
@@ -3949,4 +3950,16 @@ public class PhoneWindow extends Window implements MenuBuilder.Callback {
     public void removeScrollCaptureCallback(@NonNull ScrollCaptureCallback callback) {
         getViewRootImpl().removeScrollCaptureCallback(callback);
     }
+
+    @Override
+    @Nullable
+    public View getStatusBarBackgroundView() {
+        return mDecor != null ? mDecor.getStatusBarBackgroundView() : null;
+    }
+
+    @Override
+    @Nullable
+    public View getNavigationBarBackgroundView() {
+        return mDecor != null ? mDecor.getNavigationBarBackgroundView() : null;
+    }
 }