fix(android): always accumulate rawProps so un-flatten CREATE carries full props

Drop the earlier BackgroundStyleApplicator workaround — it targeted the
wrong layer. Fix the actual root cause in Props::initializeDynamicProps.

When a View with borderRadius + transparent backgroundColor mounts, Fabric
flattens it and no Android View is created. On a later JS update such as
backgroundColor -> opaque, the Differentiator sees the node un-flatten and
emits a CREATE mutation for a brand-new native View. FabricMountingManager
ships the props for that CREATE as newProps->rawProps.

The problem: under the default (non-accumulated) path, Props::initialize
overwrote rawProps with rawProps.toDynamic(filterObjectKeys) on every
clone — storing only the latest JS diff, not the full accumulated state.
So at un-flatten time, rawProps for the newly-concrete shadow node held
only {backgroundColor: <color>} and the Android View received only that
prop. borderRadius, borderWidth, etc. were never delivered, so the view
rendered without them.

The fix merges the previous rawProps with the incoming patch on every
clone, so rawProps always reflects the full accumulated prop set. The
existing getProps logic then ships the complete set on CREATE and the
newly-created View gets every prop it should have.

This was previously gated behind enableAccumulatedUpdatesInRawPropsAndroid.
Always running it costs an extra folly::dynamic merge per clone but fixes
a real correctness bug that could affect any view-flattening-prone
component with more than one style prop.

Author: janicduplessis

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/BackgroundStyleApplicator.kt

@@ -637,11 +637,7 @@ public object BackgroundStyleApplicator {
               compositeBackgroundDrawable.borderRadius,
               compositeBackgroundDrawable.borderInsets,
           )
-      val newComposite = compositeBackgroundDrawable.withNewBackground(background)
-      // Carry bounds over so the new BackgroundDrawable is primed with
-      // the view's real size on first draw.
-      newComposite.bounds = compositeBackgroundDrawable.bounds
-      view.background = newComposite
+      view.background = compositeBackgroundDrawable.withNewBackground(background)
       background
     }
   }

packages/react-native/ReactCommon/react/renderer/core/Props.cpp

@@ -76,15 +76,19 @@ void Props::initializeDynamicProps(
     const Props& sourceProps,
     const RawProps& rawProps,
     const std::function<bool(const std::string&)>& filterObjectKeys) {
-  if (ReactNativeFeatureFlags::enableAccumulatedUpdatesInRawPropsAndroid()) {
-    auto& oldRawProps = sourceProps.rawProps;
-    auto newRawProps = rawProps.toDynamic(filterObjectKeys);
-    auto mergedRawProps = mergeDynamicProps(
-        oldRawProps, newRawProps, NullValueStrategy::Override);
-    this->rawProps = mergedRawProps;
-  } else {
-    this->rawProps = rawProps.toDynamic(filterObjectKeys);
-  }
+  // Always merge the previous rawProps with the incoming patch so that
+  // `rawProps` reflects the full accumulated state for this shadow node.
+  // Without this, a shadow node reconstructed from a subsequent JS update
+  // only stores the latest prop diff in its rawProps. If the same shadow
+  // node later un-flattens and the Differentiator emits a CREATE mutation
+  // for it, FabricMountingManager::getProps ships only that partial diff
+  // to Java — causing props like borderRadius to never reach the newly
+  // created native view.
+  auto& oldRawProps = sourceProps.rawProps;
+  auto newRawProps = rawProps.toDynamic(filterObjectKeys);
+  auto mergedRawProps =
+      mergeDynamicProps(oldRawProps, newRawProps, NullValueStrategy::Override);
+  this->rawProps = mergedRawProps;
 }
 
 ComponentName Props::getDiffPropsImplementationTarget() const {