Bug 1488953 - Allows toolbar background paint flash along with the urlbar flickers on MacOSX in browser_windowopen.js. r=mconley

On MacOSX, especially on MacOS 10.10, the toolbar paint flush happens along
with the urlbar flickers.

Differential Revision: https://phabricator.services.mozilla.com/D34489

--HG--
extra : moz-landing-system : lando

browser/base/content/test/performance/browser_windowopen.js

@@ -21,12 +21,14 @@ const EXPECTED_REFLOWS = [
 // We'll assume the changes we are seeing are due to this focus change if
 // there are at least 5 areas that changed near the top of the screen, or if
 // the toolbar background is involved on OSX, but will only ignore this once.
-function isLikelyFocusChange(rects) {
-  if (rects.length > 5 && rects.every(r => r.y2 < 100))
-    return true;
-  if (Services.appinfo.OS == "Darwin" && rects.length == 2 && rects.every(r => r.y1 == 0 && r.h == 33))
-    return true;
-  return false;
+function filterLikelyFocusChange(rects) {
+  if (rects.length > 5 && rects.every(r => r.y2 < 100)) {
+    return [];
+  }
+  if (Services.appinfo.OS == "Darwin" && rects.length >= 2) {
+    return rects.filter(r => r.y1 != 0 || r.h != 33);
+  }
+  return rects;
 }
 
 /*
@@ -52,12 +54,15 @@ add_task(async function() {
       filter(rects, frame, previousFrame) {
         // The first screenshot we get in OSX / Windows shows an unfocused browser
         // window for some reason. See bug 1445161.
-        if (!alreadyFocused && isLikelyFocusChange(rects)) {
+        if (!alreadyFocused) {
           alreadyFocused = true;
+          let filteredRects = filterLikelyFocusChange(rects);
+          if (rects !== filteredRects) {
             todo(false,
                  "bug 1445161 - the window should be focused at first paint, " +
-               rects.toSource());
-          return [];
+                 rects.filter(r => !filteredRects.includes(r)).toSource());
+          }
+          return filteredRects;
         }
 
         return rects;