All smoke test for timeline-based is_fast measurement.

tools/telemetry/unittest_data/interaction_enabled_page.html

Index: tools/telemetry/unittest_data/interaction_enabled_page.html
diff --git a/tools/telemetry/unittest_data/interaction_enabled_page.html b/tools/telemetry/unittest_data/interaction_enabled_page.html
index 67b7ded08dfb1ba840d78e75523035a786d483d6..bdce85abd935f4fff27209b5ff962b0f7db819b1 100644
--- a/tools/telemetry/unittest_data/interaction_enabled_page.html
+++ b/tools/telemetry/unittest_data/interaction_enabled_page.html
@@ -50,17 +50,28 @@
     <script>
     'use strict';
     var jankMs = 100;
+    var slowMs = 200;
     window.jankScriptDone = false;
-    function makeJank() {
-      console.time('Interaction.JankThreadJSRun/is_responsive');
+    window.slowScriptDone = false;
+    function waitMs(ms) {
       var startTime = window.performance.now();
       var currTime = startTime;
-      while (currTime - startTime < jankMs) {
+      while (currTime - startTime < ms) {
         var currTime = window.performance.now();
       }
+    }
+    function makeJank() {
+      console.time('Interaction.JankThreadJSRun/is_responsive');
+      waitMs(jankMs);
       console.timeEnd('Interaction.JankThreadJSRun/is_responsive');
       window.jankScriptDone = true;
     }
+    function makeSlow() {
+      console.time('Interaction.SlowThreadJsRun/is_fast');
+      waitMs(slowMs);
+      console.timeEnd('Interaction.SlowThreadJsRun/is_fast');
+      window.slowScriptDone = true;
+    }
     </script>
 
   </head>
@@ -77,6 +88,9 @@
     <button type="button" id="jank-button" onclick="makeJank()">
       Click or tap this to make jank of 100ms (approximately).
     </div>
+    <button type="button" id="slow-button" onclick="makeSlow()">
+      Click or tap this to make wait 200ms (approximately).
+    </div>
 
   </body>
 </html>