Oilpan: introduce sticky forcedForTesting flag to ensure that a precise

LayoutTests/resources/js-test.js

 // svg/dynamic-updates tests set enablePixelTesting=true, as we want to dump text + pixel results
 if (self.testRunner) {
     if (self.enablePixelTesting)
         testRunner.dumpAsTextWithPixelResults();
     else
         testRunner.dumpAsText();
 }
 
 var description, debug, successfullyParsed;
 
@@ skipping 631 matching lines @@
             testPassed("Got expected error: '" + message + "'");
         else
             testFailed("Unexpected error '" + message + "'");
         expectedErrorMessage = undefined;
         return;
     }
 
     testFailed("expectError() not called before shouldHaveHadError()");
 }
 
+// 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. Therefore, tests that need to check
+// that something is dead need to use this asynchronous collectGarbage
+// function.
+function collectGarbage(callback) {
+    // Perform multiple GCs to break sequences of Oilpan Persistent handles
+    // or RefPtrs that will keep objects alive until the next GC.
+    // FIXME: Oilpan: Once everything is moved to the oilpan heap we can
+    // reduce the number of garbage collections.
+    GCController.collect();
+    setTimeout(function() {
+        GCController.collect();
+        setTimeout(function() {
+            GCController.collect();
+            setTimeout(function() {
+                GCController.collect();
+                setTimeout(callback, 0);
+            }, 0);
+        }, 0);
+    }, 0);
+}
+
 function gc() {
     if (typeof GCController !== "undefined")
         GCController.collectAll();
     else {
         var gcRec = function (n) {
             if (n < 1)
                 return {};
             var temp = {i: "ab" + i + (i / 100000)};
             temp += "foo";
             gcRec(n-1);
@@ skipping 103 matching lines @@
     testPassed = function(msg) {
         workerPort.postMessage('PASS:' + msg);
     };
     finishJSTest = function() {
         workerPort.postMessage('DONE:');
     };
     debug = function(msg) {
         workerPort.postMessage(msg);
     };
 }