Fix aggressive caching of RenderNode snapshot

Updated ImageFilter caching logic to update the snapshot
whenever the surface generation ID has changed.

Fixes: 199242895
Test: Added test to RenderNodeTests
Change-Id: I803dce35ba15a098f14dc02a479abf8b2fbae51f
diff --git a/libs/hwui/RenderNode.h b/libs/hwui/RenderNode.h
index 45a4f6c..da04762 100644
--- a/libs/hwui/RenderNode.h
+++ b/libs/hwui/RenderNode.h
@@ -396,6 +396,7 @@
      * SkImageFilter used to create the mSnapshotResult
      */
     sk_sp<SkImageFilter> mTargetImageFilter;
+    uint32_t mTargetImageFilterLayerSurfaceGenerationId = 0;
 
     /**
      * Clip bounds used to create the mSnapshotResult