Add tests for paint-timing, and move existing tests to same location

third_party/WebKit/LayoutTests/http/tests/performance-timing/paint-timing/first-contentful-image.html

Index: third_party/WebKit/LayoutTests/http/tests/performance-timing/paint-timing/first-contentful-image.html
diff --git a/third_party/WebKit/LayoutTests/fast/performance/performance-paint-timing-observable.html b/third_party/WebKit/LayoutTests/http/tests/performance-timing/paint-timing/first-contentful-image.html
similarity index 78%
copy from third_party/WebKit/LayoutTests/fast/performance/performance-paint-timing-observable.html
copy to third_party/WebKit/LayoutTests/http/tests/performance-timing/paint-timing/first-contentful-image.html
index e73b9e6e7e717a4dee0baa41fd4e0744280d91b3..9422bf748d58232cc238823090ada0befe816bdc 100644
--- a/third_party/WebKit/LayoutTests/fast/performance/performance-paint-timing-observable.html
+++ b/third_party/WebKit/LayoutTests/http/tests/performance-timing/paint-timing/first-contentful-image.html
@@ -6,7 +6,6 @@
     <script src="../../resources/testharness.js"></script>
     <script src="../../resources/testharnessreport.js"></script>
     <script>
-
     async_test(function (t) {
         var observer = new PerformanceObserver(
             t.step_func(function (entryList) {
@@ -28,9 +27,17 @@
         );
         observer.observe({entryTypes: ["paint"]});
 
-    }, "Both first-paint-timing and first-contentful-paint timing entry are observable.");
+    }, "First contentful paint fires due to image render.");
+    </script>
 
+    <script>
+    window.onload=function(){
+        var img = document.createElement("IMG");

[igrigorik, 2017/05/08 20:37:04]

Ditto here? We can check that FP happens before FCP by recording onload
timestamp?

[panicker, 2017/05/09 17:55:06]

Acknowledged.

+        img.src = "resources/circles.png";
+        document.getElementById('image').appendChild(img);
+    }
     </script>
-    <div style="background-color:black;color:white;padding:20px;">...test...</div>
+
+    <div id="image"></div>
 </body>
-</html>
+</html>