Highlight the entire line in comment context for line comments

Context has padding above and below the selected line and highlighting
the line on which the comment was created makes it clear which line
the comment was left on.

Change-Id: I2e78b9ca7df7a5674d46be3140724c49e336da23
diff --git a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
index ec7be4a..b576ad6 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
@@ -318,7 +318,18 @@
   }
 
   getHighlightRange() {
-    return this.comments?.[0]?.range;
+    const comment = this.comments?.[0];
+    if (!comment) return undefined;
+    if (comment.range) return comment.range;
+    if (comment.line) {
+      return {
+        start_line: comment.line,
+        start_character: 0,
+        end_line: comment.line,
+        end_character: 0,
+      };
+    }
+    return undefined;
   }
 
   _getDiffUrlForComment(