Expose methods to set position Start|End

Summary:
As they're were not available yet.

Emil, I'm going to wait for your diffs to land before pushing this to
avoid disruptions on your side.

Differential Revision: D3669177

fbshipit-source-id: b06f382cb89546e817a2475298cf2cad17d95a2c

java/com/facebook/csslayout/CSSNode.java

@@ -20,8 +20,10 @@ import static com.facebook.csslayout.CSSLayout.DIMENSION_WIDTH;
 import static com.facebook.csslayout.CSSLayout.POSITION_LEFT;
 import static com.facebook.csslayout.CSSLayout.POSITION_TOP;
 import static com.facebook.csslayout.Spacing.BOTTOM;
+import static com.facebook.csslayout.Spacing.END;
 import static com.facebook.csslayout.Spacing.LEFT;
 import static com.facebook.csslayout.Spacing.RIGHT;
+import static com.facebook.csslayout.Spacing.START;
 import static com.facebook.csslayout.Spacing.TOP;
 
 /**
@@ -475,6 +477,32 @@ public class CSSNode implements CSSNodeAPI<CSSNode> {
     setPositionValue(RIGHT, positionRight);
   }
 
+  /**
+   * Get this node's position start, as defined by style.
+   */
+  @Override
+  public float getPositionStart() {
+    return style.position.get(START);
+  }
+
+  @Override
+  public void setPositionStart(float positionStart) {
+    setPositionValue(START, positionStart);
+  }
+
+  /**
+   * Get this node's position end, as defined by style.
+   */
+  @Override
+  public float getPositionEnd() {
+    return style.position.get(END);
+  }
+
+  @Override
+  public void setPositionEnd(float positionEnd) {
+    setPositionValue(END, positionEnd);
+  }
+
   /**
    * Get this node's width, as defined in the style.
    */