Create YogaValue instances in Java, not C++

Summary:
@public

Passing primitive data via JNI is more efficient than passing objects.

Here, we avoid creating `YogaValue` (Java) instances via JNI, and rather pass a `long` back to Java. The instance is then created by extracting the necessary bytes on the Java side.

Reviewed By: foghina

Differential Revision: D14576755

fbshipit-source-id: 22d09ad50c3ac6c49b0a797a0dad639ea4829df9

java/tests/com/facebook/yoga/YogaNodeStylePropertiesTest.java

@@ -1,9 +1,8 @@
-/*
- *  Copyright (c) Facebook, Inc. and its affiliates.
- *
- *  This source code is licensed under the MIT license found in the LICENSE
- *  file in the root directory of this source tree.
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
  *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
  */
 package com.facebook.yoga;
 
@@ -401,6 +400,21 @@ public class YogaNodeStylePropertiesTest {
     }
   }
 
+  @Test
+  public void testNegativeMarginAssignment() {
+    final YogaNode node = createNode();
+    for (YogaEdge edge : YogaEdge.values()) {
+      node.setMargin(edge, -25);
+      assertEquals(new YogaValue(-25, YogaUnit.POINT), node.getMargin(edge));
+
+      node.setMarginPercent(edge, -5);
+      assertEquals(new YogaValue(-5, YogaUnit.PERCENT), node.getMargin(edge));
+
+      node.setMarginAuto(edge);
+      assertEquals(YogaValue.AUTO, node.getMargin(edge));
+    }
+  }
+
   @Test
   public void testMarginPointAffectsLayout() {
     final YogaNode node = style().margin(YogaEdge.TOP, 42).node();