Use event path to detect if anchor has been clicked in WebUIs.

chrome/test/data/webui/md_history/history_list_test.js

Index: chrome/test/data/webui/md_history/history_list_test.js
diff --git a/chrome/test/data/webui/md_history/history_list_test.js b/chrome/test/data/webui/md_history/history_list_test.js
index f6c913babf426384bae2a4d68f7edf8b6bc45fb5..e83a9dd27d1dc13b72b2dcc5f3243eb4d1397fae 100644
--- a/chrome/test/data/webui/md_history/history_list_test.js
+++ b/chrome/test/data/webui/md_history/history_list_test.js
@@ -267,10 +267,29 @@ cr.define('md_history.history_list_test', function() {
         });
       });
 
+      test('clicking file:// url sends message to chrome', function(done) {
+        var fileURL = 'file:///home/myfile';
+        app.historyResult(createHistoryInfo(), [
+          createHistoryEntry('2016-03-15', fileURL),
+        ]);
+        flush().then(function() {
+          var items =
+              Polymer.dom(element.root).querySelectorAll('history-item');
+
+          registerMessageCallback('navigateToUrl', this, function(info) {

[Dan Beam, 2016/08/02 06:02:43]

registerMessageCallback() is a bummer.  didn't know you guys were using this in
new code...

[calamity, 2016/08/08 05:06:43]

Any alternatives?

[Dan Beam, 2016/08/08 21:27:59]

don't call chrome.send() directly from your code.  instead make a "BrowserProxy"
thing like we do in settings

+            assertEquals(fileURL, info[0]);
+            done();
+          });
+
+          MockInteractions.tap(items[0].$.title);
+        });
+      });
+
       teardown(function() {
         element.historyData_ = [];
         registerMessageCallback('removeVisits', this, undefined);
         registerMessageCallback('queryHistory', this, function() {});
+        registerMessageCallback('navigateToUrl', this, function() {});

[Dan Beam, 2016/08/02 06:02:43]

why is this necessary?

[calamity, 2016/08/08 05:06:43]

undefined would work here too. We need to tear down the message callback to
prevent it from running on subsequent calls during other tests.

         app.queryState_.queryingDisabled = true;
         app.set('queryState_.searchTerm', '');
         return flush();