Oilpan: introduce sticky forcedForTesting flag to ensure that a precise

LayoutTests/svg/animations/smil-leak-element-instances.svg

 <svg id="svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" onload="load()">
 <defs>
     <rect id="rect" width="100" height="100" />
 </defs>
 <g id="g"/>
 <text x="50" y="50" id="log"/>
 <script id="script">
 <![CDATA[
 
 var g = document.getElementById("g");
@@ skipping 14 matching lines @@
     anim.setAttribute("to", "0");
     anim.setAttribute("begin", "0s");
     anim.setAttribute("dur", "10.0s");
     anim.setAttribute("repeatCount", 1);
 
     use.appendChild(anim);
 
     return use;
 }
 
+// With Oilpan tests that rely on garbage collection need to go through
+// the event loop in order to get precise garbage collections. Oilpan
+// uses conservative stack scanning when not at the event loop and that
+// can artificially keep objects alive. Therfore, test that need to check

[wibling-chromium, 2014/04/01 13:26:09]

Ditto.

[Mads Ager (chromium), 2014/04/01 13:45:38]

Done.

+// that something is dead need to use this asynchronous collectGarbage
+// function.
+function collectGarbage(callback) {
+    GCController.collect();
+    setTimeout(function() {
+        GCController.collect();
+        setTimeout(function() {
+            GCController.collect();
+            setTimeout(function() {
+                GCController.collect();
+                setTimeout(callback, 0);
+            }, 0);
+        }, 0);
+    }, 0);
+}
+
 function cleanup() {
     // Collect garbage before recording starting live node count, in case there are live elements from previous tests.
-    GCController.collectAll();
-    var originalLiveElements = internals.numberOfLiveNodes();
+    collectGarbage(function() {
+        var originalLiveElements = internals.numberOfLiveNodes();
 
-    while (g.hasChildNodes())
-        g.removeChild(g.lastChild);
+        while (g.hasChildNodes())
+            g.removeChild(g.lastChild);
 
-    GCController.collectAll();
+        collectGarbage(function() {
+            // This is 400 instead of 200 as it creates shadow tree elements.
+            var liveDelta = originalLiveElements - internals.numberOfLiveNodes() - 400;
+            if (liveDelta == 0)
+                log("PASS");
+            else
+                log("FAIL: " + liveDelta + " extra live node(s)");
 
-    // This is 400 instead of 200 as it creates shadow tree elements.
-    var liveDelta = originalLiveElements - internals.numberOfLiveNodes() - 400;
-    if (liveDelta == 0)
-        log("PASS");
-    else
-        log("FAIL: " + liveDelta + " extra live node(s)");
-
-    testRunner.notifyDone();
+            testRunner.notifyDone();
+        });
+    });
 }

[wibling-chromium, 2014/04/01 13:26:09]

Also can't we waitUntilDone here to not exit until the gc is complete?

[Mads Ager (chromium), 2014/04/01 13:45:38]

Already done in the load function.

 
 function startTest() {
     // Hold a reference to rect.x.baseVal on the root instance.
     xBaseVal = document.getElementById("rect").x.baseVal;
 
     for (var i = 0; i < 100; i++)
         g.appendChild(createAnimatedRectInstance());
 
     setTimeout(cleanup, 0);
 }
 
 function load() {
     if (window.testRunner && window.GCController && window.internals) {
         testRunner.dumpAsText();
         testRunner.waitUntilDone();
     } else {
         log("This test only works when run with the testRunner, GCController, and internals available.");
         return;
     }
 
     setTimeout(startTest, 0);
 }
 ]]>
 </script>
 </svg>