Fix GH-41226 by suppressing path adjustment when not actually drawing…

… a border (#46239)

Summary:
When not drawing a border, the mGapBetweenPaths adjustment can create noticable pixelation when drawing curves through a low number of pixels.  This is noticable mostly on buttons and such on low-dpi devices.  This fix only applies the fix if clipping for the border radius is done.

When drawing small radius rounded backgrounds (e.g. to draw a circle or button) we see visible pixelation (see [GH-41226](#41226)) This is particularly noticable on low DPI devices.

## Changelog:

[ANDROID] [FIXED] - Don't use mGapBetweenPaths if not drawing a border

Pull Request resolved: #46239

Test Plan:
Built an android app that directly uses CSSBackgroundDrawable to draw a background and verified repro of this issue.
![pre-fix](https://github.com/user-attachments/assets/e56a41b1-60f6-4953-9e91-b95a3380f2d7)
Then modified the code according to this PR and verified that anti-aliasing is appropriately applied
![fix](https://github.com/user-attachments/assets/b6b1aecf-a713-4e0a-9759-82c2dd862991)

Reviewed By: NickGerleman

Differential Revision: D61925281

Pulled By: jorge-cab

fbshipit-source-id: 93014629d031bd0d716cd3bb11e2c294dedad639

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/drawable/CSSBackgroundDrawable.java

@@ -645,6 +645,7 @@ private void updatePath() {
     }
 
     // Clip border ONLY if its color is non transparent
+    float pathAdjustment = 0f;
     if (Color.alpha(colorLeft) != 0
         && Color.alpha(colorTop) != 0
         && Color.alpha(colorRight) != 0
@@ -655,6 +656,10 @@ private void updatePath() {
       mInnerClipTempRectForBorderRadius.bottom -= borderWidth.bottom;
       mInnerClipTempRectForBorderRadius.left += borderWidth.left;
       mInnerClipTempRectForBorderRadius.right -= borderWidth.right;
+
+      // only close gap between border and main path if we draw the border, otherwise
+      // we wind up pixelating small pixel-radius curves
+      pathAdjustment = mGapBetweenPaths;
     }
 
     mTempRectForCenterDrawPath.top += borderWidth.top * 0.5f;
@@ -709,10 +714,10 @@ private void updatePath() {
     // (mInnerClipTempRectForBorderRadius), ensuring the border can be
     // drawn on top without the gap.
     mBackgroundColorRenderPath.addRoundRect(
-        mInnerClipTempRectForBorderRadius.left - mGapBetweenPaths,
-        mInnerClipTempRectForBorderRadius.top - mGapBetweenPaths,
-        mInnerClipTempRectForBorderRadius.right + mGapBetweenPaths,
-        mInnerClipTempRectForBorderRadius.bottom + mGapBetweenPaths,
+        mInnerClipTempRectForBorderRadius.left - pathAdjustment,
+        mInnerClipTempRectForBorderRadius.top - pathAdjustment,
+        mInnerClipTempRectForBorderRadius.right + pathAdjustment,
+        mInnerClipTempRectForBorderRadius.bottom + pathAdjustment,
         new float[] {
           innerTopLeftRadiusX,
           innerTopLeftRadiusY,