Compositing: avoid flakes in overflow-positioning.html

third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html

Index: third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html
diff --git a/third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html b/third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html
index d0a1874386f5de743151d78a57cf4e94fc6ef88f..4e8894fad49dbea3ac53cd968064746d64f9ce91 100644
--- a/third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html
+++ b/third_party/WebKit/LayoutTests/compositing/overflow/overflow-positioning.html
@@ -40,7 +40,7 @@
     height: 150px;
     width: 150px;
     background-color: green;
-    transition: transform 1000s;
+    transition: transform 1s;
   }
   
   #mover:hover {
@@ -54,18 +54,22 @@
     if (window.testRunner)
       testRunner.waitUntilDone();
 
+    function waitForCompositor() {
+      return document.body.animate({opacity: [1, 1]}, 1).finished;
+    }
+
     function startTest()
     {
-      window.setTimeout(function() {
-        var mover = document.getElementById('mover');
-        mover.className = 'moving';
-        
-        window.setTimeout(function() {
-          if (window.testRunner)
-            testRunner.notifyDone();
-        }, 0);
-        
-      }, 0);
+      var mover = document.getElementById('mover');
+      getComputedStyle(mover).transform; // Force style recalc
+      mover.className = 'moving';
+      internals.pauseAnimations(0);

[wkorman, 2017/02/17 23:12:38]

This is usually behind an if (window.internals), see for example
animations/interpolation/left-zoomed-interpolation.html.

Just so that when running locally in content shell or browser one doesn't see JS
error.

[Eric Willigers, 2017/02/20 02:28:51]

Done.

+
+      waitForCompositor().then(() => {
+        if (window.testRunner) {
+          testRunner.notifyDone();
+        }
+      });
     }
 
     window.addEventListener('load', startTest, false);