latency: use listeners to detect changes in projects and tests

The current method is non-standard, or considered obsolete, so let's
use the normal method, and hopefully it will resolve some issues that
are hit by some users.

Suggested-by: @ivyl / Arkadiusz Hiler

site-publishing/assets/latency.js

@@ -108,7 +108,6 @@ function pw_test_latency_fetch(project, tests_target, plot_target, weeks, defaul
             var option = document.createElement("option");
             option.text = test_name;
             option.value = test_name.trim();
-            option.addEventListener('click', function(e) {pw_latency_plot(e.target.value);});
             select_tests.appendChild(option);
         });
         select_tests.disabled = false;

site/latency.md

@@ -7,7 +7,7 @@ This view enables you to visualize the latency between a patch has been sent and
 
 <div class="inline-form">
     Select a project / test to get statistics for:
-    <select id="projects" onchange="pw_test_latency_fetch(this.options[this.selectedIndex].value, 'tests', 'plot', 1);">
+    <select id="projects">
         <option value="" disabled selected hidden>Please select a project</option>
     </select>
     <select id="tests" disabled>
@@ -62,12 +62,12 @@ This view enables you to visualize the latency between a patch has been sent and
     };
 
     // Add all the available projects
-    var e = document.getElementById('projects');
+    var select_projects = document.getElementById('projects');
     for (let p_name in projects) {
         var o = document.createElement("option");
         o.value = p_name;
         o.text = projects[p_name].name;
-        e.appendChild(o);
+        select_projects.appendChild(o);
     }
 
     // If a project has been set in the URL, select it
@@ -76,4 +76,13 @@ This view enables you to visualize the latency between a patch has been sent and
         pw_test_latency_fetch(default_project, 'tests', 'plot', 1, get_url_parameter('test', undefined));
         document.getElementById('projects').value = default_project;
     }
+
+    select_projects.addEventListener('change', function() {
+        pw_test_latency_fetch(this.options[this.selectedIndex].value, 'tests', 'plot', 1);
+    });
+
+    var select_tests = document.getElementById('tests');
+    select_tests.addEventListener('change', function() {
+        pw_latency_plot(this.options[this.selectedIndex].value);
+    });
 </script>