[Telemetry] Improve logging on media measurement tests.

tools/perf/metrics/media.js

Index: tools/perf/metrics/media.js
diff --git a/tools/perf/metrics/media.js b/tools/perf/metrics/media.js
index 792e755de8017dfd1acd0db73807ef97a0b05bfa..834161052f75f42059e2590e3a2a84ecd067834c 100644
--- a/tools/perf/metrics/media.js
+++ b/tools/perf/metrics/media.js
@@ -63,10 +63,10 @@
   HTMLMediaMetric.prototype.constructor = HTMLMediaMetric;
 
   HTMLMediaMetric.prototype.setID = function() {
-    if (this.element.src)
-      this.id = this.element.src.substring(this.element.src.lastIndexOf("/")+1);
-    else if (this.element.id)
+    if (this.element.id)
       this.id = this.element.id;
+    else if (this.element.src)
+      this.id = this.element.src.substring(this.element.src.lastIndexOf("/")+1);
     else
       this.id = 'media_' + window.__globalCounter++;
   };