Delay resetting image animation, if possible.

third_party/WebKit/Source/core/fetch/ImageResource.cpp

Index: third_party/WebKit/Source/core/fetch/ImageResource.cpp
diff --git a/third_party/WebKit/Source/core/fetch/ImageResource.cpp b/third_party/WebKit/Source/core/fetch/ImageResource.cpp
index 81db13640f8150ed4554bcf6542607cb4925b564..956fc6db413a3f5e040b309bc22dc98338aad73a 100644
--- a/third_party/WebKit/Source/core/fetch/ImageResource.cpp
+++ b/third_party/WebKit/Source/core/fetch/ImageResource.cpp
@@ -206,10 +206,23 @@ void ImageResource::destroyDecodedDataIfPossible()
     }
 }
 
-void ImageResource::allClientsAndObserversRemoved()
+void ImageResource::doResetAnimation()
 {
-    if (m_image && !errorOccurred())
+    if (m_image)
         m_image->resetAnimation();
+}
+
+void ImageResource::allClientsAndObserversRemoved()
+{
+    if (m_image && !errorOccurred()) {
+        // If possible, delay the resetting until back at the event loop.
+        // Doing so after a conservative GC prevents resetAnimation() from
+        // upsetting ongoing animation updates (crbug.com/613709)
+        if (!ThreadHeap::willObjectBeLazilySwept(this))

[haraken, 2016/05/24 15:40:54]

Hmm, I'm not really happy about using ThreadHeap::willObjectBeLazilySwept since
it can return a wrong result (as we discussed previously).

Would it be possible to introduce a flag to ImageResource and set it in a
pre-finalizer? Then we can check the flag here to see if the ImageResource is
going to be collected or not.

[sof, 2016/05/24 15:47:20]

As this method will be called by another object's prefinalizer, I don't think
that scheme will work.

As long as willBeLazilySwept() returns true while that other object's
prefinalizer is running, that's sufficient. We could add that as a flag to
ThreadState (== is running prefinalizers), I suppose.

+            Platform::current()->currentThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, bind(&ImageResource::doResetAnimation, CrossThreadWeakPersistentThisPointer<ImageResource>(this)));
+        else
+            m_image->resetAnimation();
+    }
     if (m_multipartParser)
         m_multipartParser->cancel();
     Resource::allClientsAndObserversRemoved();