Don't reset LoadEventProgress if frame unload has already started.

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h

Index: third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h b/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h
index 6423d5ad6b2477f8b6b3c67b064cb87a6b814362..4dda878fed1a4848d156c2c7c9cbd2608f99ceb7 100644
--- a/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h
@@ -109,21 +109,25 @@ DEFINE_ELEMENT_TYPE_CASTS(HTMLFrameOwnerElement, isFrameOwnerElement());
 class SubframeLoadingDisabler {
     STACK_ALLOCATED();
 public:
-    explicit SubframeLoadingDisabler(Node& root)
+    explicit SubframeLoadingDisabler(Node& root) : SubframeLoadingDisabler(&root)
+    {
+    }
+
+    explicit SubframeLoadingDisabler(Node* root)

[Nate Chapin, 2016/02/03 23:25:14]

Do we have to have constructors for both a pointer and a reference? That seems
kind of lame.

[dcheng, 2016/02/03 23:33:31]

A pre-Oilpan alternative is to just keep the reference constructor. Then we
could do something like:

OwnPtr<SubframeLoadingDisabler> disabler;
if (m_frame->document())
  disabler.reset(new SubframeLoadingDisabler(*m_frame->document()));

But this doesn't work with Oilpan: SubframeLoadingDisabler would have to become
a garbage collected class, but then it references a garbage collected member in
the destructor, and all sorts of complexity.

I just added the pointer version because it is still nice to assert that the
passed in Node* is not null (which is true 99% of the time).

An alternative (which I want to try following up on) is to rearrange
prepareForCommit() to make it so we only take this branch if document is not
null, but that's a bigger change and harder to merge.

         : m_root(root)
     {
-        disabledSubtreeRoots().add(m_root);
+        if (m_root)
+            disabledSubtreeRoots().add(m_root);
     }
 
     ~SubframeLoadingDisabler()
     {
-        disabledSubtreeRoots().remove(m_root);
+        if (m_root)
+            disabledSubtreeRoots().remove(m_root);
     }
 
     static bool canLoadFrame(HTMLFrameOwnerElement& owner)
     {
-        if (owner.document().unloadStarted())
-            return false;
         for (Node* node = &owner; node; node = node->parentOrShadowHostNode()) {
             if (disabledSubtreeRoots().contains(node))
                 return false;