1 files changed, 138 insertions, 0 deletions
diff --git a/image/test/browser/browser_bug666317.js b/image/test/browser/browser_bug666317.js
new file mode 100644
index 0000000000..7f58c61c56
--- /dev/null
+++ b/image/test/browser/browser_bug666317.js
@@ -0,0 +1,138 @@
+waitForExplicitFinish();
+
+var pageSource =
+  "<html><body>" +
+  '<img id="testImg" src="' +
+  TESTROOT +
+  'big.png">' +
+  "</body></html>";
+
+var oldDiscardingPref, oldTab, newTab;
+var prefBranch = Services.prefs.getBranch("image.mem.");
+
+var gWaitingForDiscard = false;
+var gScriptedObserver;
+var gClonedRequest;
+
+function ImageObserver(decodeCallback, discardCallback) {
+  this.decodeComplete = function onDecodeComplete(aRequest) {
+    decodeCallback();
+  };
+
+  this.discard = function onDiscard(request) {
+    if (!gWaitingForDiscard) {
+      return;
+    }
+
+    this.synchronous = false;
+    discardCallback();
+  };
+
+  this.synchronous = true;
+}
+
+function currentRequest() {
+  let img = gBrowser
+    .getBrowserForTab(newTab)
+    .contentWindow.document.getElementById("testImg");
+  return img.getRequest(Ci.nsIImageLoadingContent.CURRENT_REQUEST);
+}
+
+function isImgDecoded() {
+  let request = currentRequest();
+  return !!(request.imageStatus & Ci.imgIRequest.STATUS_DECODE_COMPLETE);
+}
+
+// Ensure that the image is decoded by drawing it to a canvas.
+function forceDecodeImg() {
+  let doc = gBrowser.getBrowserForTab(newTab).contentWindow.document;
+  let img = doc.getElementById("testImg");
+  let canvas = doc.createElement("canvas");
+  let ctx = canvas.getContext("2d");
+  ctx.drawImage(img, 0, 0);
+}
+
+function runAfterAsyncEvents(aCallback) {
+  function handlePostMessage(aEvent) {
+    if (aEvent.data == "next") {
+      window.removeEventListener("message", handlePostMessage);
+      aCallback();
+    }
+  }
+
+  window.addEventListener("message", handlePostMessage);
+
+  // We'll receive the 'message' event after everything else that's currently in
+  // the event queue (which is a stronger guarantee than setTimeout, because
+  // setTimeout events may be coalesced). This lets us ensure that we run
+  // aCallback *after* any asynchronous events are delivered.
+  window.postMessage("next", "*");
+}
+
+function test() {
+  // Enable the discarding pref.
+  oldDiscardingPref = prefBranch.getBoolPref("discardable");
+  prefBranch.setBoolPref("discardable", true);
+
+  // Create and focus a new tab.
+  oldTab = gBrowser.selectedTab;
+  newTab = BrowserTestUtils.addTab(gBrowser, "data:text/html," + pageSource);
+  gBrowser.selectedTab = newTab;
+
+  // Run step2 after the tab loads.
+  gBrowser.getBrowserForTab(newTab).addEventListener("pageshow", step2);
+}
+
+function step2() {
+  // Create the image observer.
+  var observer = new ImageObserver(
+    () => runAfterAsyncEvents(step3), // DECODE_COMPLETE
+    () => runAfterAsyncEvents(step5)
+  ); // DISCARD
+  gScriptedObserver = Cc["@mozilla.org/image/tools;1"]
+    .getService(Ci.imgITools)
+    .createScriptedObserver(observer);
+
+  // Clone the current imgIRequest with our new observer.
+  var request = currentRequest();
+  gClonedRequest = request.clone(gScriptedObserver);
+
+  // Check that the image is decoded.
+  forceDecodeImg();
+
+  // The DECODE_COMPLETE notification is delivered asynchronously. ImageObserver will
+  // eventually call step3.
+}
+
+function step3() {
+  ok(isImgDecoded(), "Image should initially be decoded.");
+
+  // Focus the old tab, then fire a memory-pressure notification.  This should
+  // cause the decoded image in the new tab to be discarded.
+  gBrowser.selectedTab = oldTab;
+
+  // Allow time to process the tab change.
+  runAfterAsyncEvents(step4);
+}
+
+function step4() {
+  gWaitingForDiscard = true;
+
+  var os = Services.obs;
+  os.notifyObservers(null, "memory-pressure", "heap-minimize");
+
+  // The DISCARD notification is delivered asynchronously. ImageObserver will
+  // eventually call step5. (Or else, sadly, the test will time out.)
+}
+
+function step5() {
+  ok(true, "Image should be discarded.");
+
+  // And we're done.
+  gBrowser.removeTab(newTab);
+  prefBranch.setBoolPref("discardable", oldDiscardingPref);
+
+  gClonedRequest.cancelAndForgetObserver(0);
+
+  finish();
+}