Support gainmap HW copy.

- for Bitmap::allocateHardwareBitmap to create and upload a hardware
  version of the gainmap.

Bug: 267216439
Test: android.graphics.cts.BitmapFactoryTest,
android.graphics.cts.BitmapRegionDecoderTest,
android.graphics.cts.ImageDecoderTest, android.graphics.cts.GainmapTest

Change-Id: Ie080896425dc82a605b2bc41e97ddc2420f5328a
diff --git a/libs/hwui/Gainmap.h b/libs/hwui/Gainmap.h
index 765f98a..3bc183a 100644
--- a/libs/hwui/Gainmap.h
+++ b/libs/hwui/Gainmap.h
@@ -27,6 +27,7 @@
 public:
     SkGainmapInfo info;
     sk_sp<Bitmap> bitmap;
+    static sp<Gainmap> allocateHardwareGainmap(const sp<Gainmap>& srcGainmap);
 };
 
 }  // namespace android::uirenderer