Load and draw bitmap only once with ImageWallpaper

Given that ImageWallpaper uses surface.SetFixedSize with the dimensions
of the image, and that WallpaperController moves the without redrawing
the bitmap (e.g. in case of rotation/unfold), the bitmap only needs to
be drawn once (in theory).

Bug: 288582051
Bug: 265018814
Test: manual on foldable: fold, unfold, rotate, with one or two
ImageWallpaper engines
Test: atest ImageWallpaperTest

Change-Id: I1a61c5d30c5f4d6abff4eac76195b74dfb18fe6f

packages/SystemUI/src/com/android/systemui/wallpapers/ImageWallpaper.java

@@ -109,6 +109,7 @@ public class ImageWallpaper extends WallpaperService {
         private WallpaperManager mWallpaperManager;
         private final WallpaperLocalColorExtractor mWallpaperLocalColorExtractor;
         private SurfaceHolder mSurfaceHolder;
+        private boolean mDrawn = false;
         @VisibleForTesting
         static final int MIN_SURFACE_WIDTH = 128;
         @VisibleForTesting
@@ -238,6 +239,7 @@ public class ImageWallpaper extends WallpaperService {
 
         private void drawFrameSynchronized() {
             synchronized (mLock) {
+                if (mDrawn) return;
                 drawFrameInternal();
             }
         }
@@ -275,6 +277,7 @@ public class ImageWallpaper extends WallpaperService {
                 Rect dest = mSurfaceHolder.getSurfaceFrame();
                 try {
                     canvas.drawBitmap(bitmap, null, dest, null);
+                    mDrawn = true;
                 } finally {
                     surface.unlockCanvasAndPost(canvas);
                 }