[Android] Fix: incorrect line-height calculation

ReactAndroid/src/main/java/com/facebook/react/views/text/CustomLineHeightSpan.java

@@ -55,10 +55,12 @@ public void chooseHeight(
       // Show proportionally additional ascent / top & descent / bottom
       final int additional = mHeight - (-fm.top + fm.bottom);
 
-      fm.top -= additional / 2;
-      fm.ascent -= additional / 2;
-      fm.descent += additional / 2;
-      fm.bottom += additional / 2;
+      // Round up for the negative values and down for the positive values  (arbritary choice)
+      // So that bottom - top equals additional even if it's an odd number.
+      fm.top -= Math.ceil(additional / 2.0f);
+      fm.bottom += Math.floor(additional / 2.0f);
+      fm.ascent = fm.top;
+      fm.descent = fm.bottom;
     }
   }
 }

ReactAndroid/src/test/java/com/facebook/react/views/text/CustomLineHeightSpanTest.java

@@ -13,18 +13,35 @@
 public class CustomLineHeightSpanTest {
 
   @Test
-  public void shouldIncreaseAllMetricsProportionally() {
+  public void evenLineHeightShouldIncreaseAllMetricsProportionally() {
     CustomLineHeightSpan customLineHeightSpan = new CustomLineHeightSpan(22);
     Paint.FontMetricsInt fm = new Paint.FontMetricsInt();
     fm.top = -10;
     fm.ascent = -5;
     fm.descent = 5;
     fm.bottom = 10;
     customLineHeightSpan.chooseHeight("Hi", 0, 2, 0, 0, fm);
+    // Since line height is even it should be equally added to top and bottom.
     assertThat(fm.top).isEqualTo(-11);
-    assertThat(fm.ascent).isEqualTo(-6);
-    assertThat(fm.descent).isEqualTo(6);
+    assertThat(fm.ascent).isEqualTo(-11);
+    assertThat(fm.descent).isEqualTo(11);
     assertThat(fm.bottom).isEqualTo(11);
+    assertThat(fm.bottom - fm.top).isEqualTo(22);
+  }
+
+  @Test
+  public void oddLineHeightShouldAlsoWork() {
+    CustomLineHeightSpan customLineHeightSpan = new CustomLineHeightSpan(23);
+    Paint.FontMetricsInt fm = new Paint.FontMetricsInt();
+    fm.top = -10;
+    fm.ascent = -5;
+    fm.descent = 5;
+    fm.bottom = 10;
+    customLineHeightSpan.chooseHeight("Hi", 0, 2, 0, 0, fm);
+    // Only test that the sum is correct so the implementation
+    // is free to add the odd value either on top or bottom.
+    assertThat(fm.descent - fm.ascent).isEqualTo(23);
+    assertThat(fm.bottom - fm.top).isEqualTo(23);
   }
 
   @Test