Add backup element queue to CustomElementReactionStack

third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp

Index: third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp b/third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp
index 817a91900e441d1eedb4811fce7e46ddebee5e99..30d315fed3412e0581c4301b18fe293c1a6f26ff 100644
--- a/third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp
@@ -13,15 +13,17 @@ namespace blink {
 
 CEReactionsScope* CEReactionsScope::s_topOfStack = nullptr;
 
-void CEReactionsScope::enqueue(
-    Element* element,
-    CustomElementReaction* reaction)
+CustomElementReactionStack* CEReactionsScope::currentCustomElementReactionStack(
+    Element* element)
 {
-    if (!m_frameHost.get()) {
-        m_frameHost = element->document().frameHost();
-        m_frameHost->customElementReactionStack().push();
+    if (!s_topOfStack)

[dominicc (has gone to gerrit), 2016/06/28 03:37:13]

I don't like this, because it looks like a getter but it side-effects the
reactions scope; m_frameHost is used later as a flag meaning there is work to
do.

Maybe you should make this an explicit protocol, like
CEReactionsScope::setShouldPopReactionStack() or something.

BTW, could we add an assertion that if m_frameHost.get() then
element->document().frameHost() == m_frameHost?

[kojii, 2016/06/28 04:19:04]

By moving to CustomElement::enqueue(), this was reverted.
Done.

+        return nullptr;
+
+    if (!s_topOfStack->m_frameHost.get()) {
+        s_topOfStack->m_frameHost = element->document().frameHost();
+        s_topOfStack->m_frameHost->customElementReactionStack().push();
     }
-    m_frameHost->customElementReactionStack().enqueue(element, reaction);
+    return &s_topOfStack->m_frameHost->customElementReactionStack();
 }
 
 void CEReactionsScope::invokeReactions()