Fix types of line

Since we have compilation off, these are merely documentation, but that
`number` through me off quite a bit - definitely worth fixing.

Change-Id: Ic5ba1daeaad8c68ef3460ccb53f9f4ec6de0fcfa

polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js

@@ -353,7 +353,7 @@
   };
 
   /**
-   * @param {number} line
+   * @param {GrDiffLine} line
    * @param {string=} opt_side
    * @return {!Object}
    */

polygerrit-ui/app/elements/diff/gr-diff/gr-diff-line.js

@@ -25,8 +25,10 @@
     this.highlights = [];
   }
 
+  /** @type {number|string} */
   GrDiffLine.prototype.afterNumber = 0;
 
+  /** @type {number|string} */
   GrDiffLine.prototype.beforeNumber = 0;
 
   GrDiffLine.prototype.contextGroup = null;