[telemetry] Clean up image decoding benchmark

tools/perf/page_sets/tough_image_cases.json

Index: tools/perf/page_sets/tough_image_cases.json
diff --git a/tools/perf/page_sets/tough_image_cases.json b/tools/perf/page_sets/tough_image_cases.json
index 036233c805456cf3bcf80fdfce1ad15757701851..9077e6a354ee27fa035ff20c8d37a3bcf5d588ee 100644
--- a/tools/perf/page_sets/tough_image_cases.json
+++ b/tools/perf/page_sets/tough_image_cases.json
@@ -1,8 +1,23 @@
 {
-  "description": "A collection of image decoding performance tests",
+  "description": "**THIS IS OBSOLETE, EDIT image_decoding_benchmark.json instead***",
   "pages": [
-    {"url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?gif"},
-    {"url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?jpg"},
-    {"url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?png"}
+    {
+      "url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?gif",
+      "post_navigate_javascript_to_execute": "runBenchmark();",
+      "wait_for_javascript_expression": "isDone",
+      "image_decoding_benchmark_limit_results_to_min_iterations": true
+    },
+    {
+      "url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?jpg",
+      "post_navigate_javascript_to_execute": "runBenchmark();",
+      "wait_for_javascript_expression": "isDone",
+      "image_decoding_benchmark_limit_results_to_min_iterations": true
+    },
+    {
+      "url": "file:///../../../chrome/test/data/image_decoding/image_decoding.html?png",
+      "post_navigate_javascript_to_execute": "runBenchmark();",
+      "wait_for_javascript_expression": "isDone",
+      "image_decoding_benchmark_limit_results_to_min_iterations": true
+    }
   ]
 }