Rewrite on-tap to on-click

Polymer recommends to prefer click events over Polymer tap events.
Performance on initializing on-click is much better than on-tap.

https://polymer-library.polymer-project.org/2.0/docs/devguide/gesture-events

Change-Id: I0aec1ddcc9ad74f7880e7fd7ca0689b5c8c84796
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
index 2b12932..32fa7e5 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
@@ -406,10 +406,10 @@
         Prevented render because "Whole file" is enabled and this diff is very
         large (about [[_diffLength]] lines).
       </p>
-      <gr-button on-tap="_handleLimitedBypass">
+      <gr-button on-click="_handleLimitedBypass">
         Render with limited context
       </gr-button>
-      <gr-button on-tap="_handleFullBypass">
+      <gr-button on-click="_handleFullBypass">
         Render anyway (may be slow)
       </gr-button>
     </div>