Improve picture capture debug path

* Fixes hardware bitmap capture
* Fixes mutable bitmap capture (no flickering)
* Adds basic single-frame LRU cache to avoid
  repeated readbacks of GPU resources
* Does up-front readback of GPU resources
* Moves serialization off RenderThread again thanks
  to up-front readback avoiding needing GPU access
  off-thread
* Reduces RAM usage & improves performance by serializing
  directly to output stream instead of first copying to
  a byte[]

Bug: 174223722
Test: PictureCaptureDemo mirrors the content
Change-Id: If7ec208b61d5b917e82087cc312880fc5a38c943
diff --git a/libs/hwui/Readback.h b/libs/hwui/Readback.h
index 4cb4bd8..da25269 100644
--- a/libs/hwui/Readback.h
+++ b/libs/hwui/Readback.h
@@ -50,6 +50,7 @@
     CopyResult copySurfaceInto(ANativeWindow* window, const Rect& srcRect, SkBitmap* bitmap);
 
     CopyResult copyHWBitmapInto(Bitmap* hwBitmap, SkBitmap* bitmap);
+    CopyResult copyImageInto(const sk_sp<SkImage>& image, SkBitmap* bitmap);
 
     CopyResult copyLayerInto(DeferredLayerUpdater* layer, SkBitmap* bitmap);