Call preventDefault in all on-tap events that show a dialog.

chrome/browser/resources/settings/about_page/detailed_build_info.js

Index: chrome/browser/resources/settings/about_page/detailed_build_info.js
diff --git a/chrome/browser/resources/settings/about_page/detailed_build_info.js b/chrome/browser/resources/settings/about_page/detailed_build_info.js
index ab301700ec3036ca490badaaf5987f80ffab750f..e6d93374c541730f794152e6dcca046afd56c3ed 100644
--- a/chrome/browser/resources/settings/about_page/detailed_build_info.js
+++ b/chrome/browser/resources/settings/about_page/detailed_build_info.js
@@ -55,8 +55,12 @@ Polymer({
     return version.length > 0;
   },
 
-  /** @private */
-  onChangeChannelTap_: function() {
+  /**
+   * @param {!Event} e The polymer event.

[dpapad, 2016/12/07 20:00:50]

Nit (optional): Perhaps drop the "The polymer event" comment from everywhere
since it does not add much useful info.

[hcarmona, 2016/12/08 20:12:50]

Done.

+   * @private
+   */
+  onChangeChannelTap_: function(e) {
+    e.preventDefault();
     this.showChannelSwitcherDialog_ = true;
     // Async to wait for dialog to appear in the DOM.
     this.async(function() {