From 053f3e648d3a02b82dc96503a8a65c11d69d1b9d Mon Sep 17 00:00:00 2001
From: Sean Feng <sefeng@mozilla.com>
Date: Tue, 17 Mar 2020 14:53:00 +0000
Subject: [PATCH] Bug 1377999 - Make nsIContent to declare a final
 DeleteCycleCollectable r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D63263

--HG--
extra : moz-landing-system : lando
---
 dom/base/FragmentOrElement.cpp |  7 +++++--
 dom/base/nsIContent.h          |  5 ++++-
 xpcom/base/nsISupportsImpl.h   | 25 +++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index 6fd282796ccd..e5ce70618f36 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -144,8 +144,11 @@ NS_INTERFACE_MAP_BEGIN(nsIContent)
 NS_INTERFACE_MAP_END
 
 NS_IMPL_MAIN_THREAD_ONLY_CYCLE_COLLECTING_ADDREF(nsIContent)
-NS_IMPL_MAIN_THREAD_ONLY_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(
-    nsIContent, LastRelease())
+
+NS_IMPL_DOMARENA_DESTROY(nsIContent)
+
+NS_IMPL_MAIN_THREAD_ONLY_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE_AND_DESTROY(
+    nsIContent, LastRelease(), Destroy())
 
 nsIContent* nsIContent::FindFirstNonChromeOnlyAccessContent() const {
   // This handles also nested native anonymous content.
diff --git a/dom/base/nsIContent.h b/dom/base/nsIContent.h
index d557b02085fc..16c2ead2d5df 100644
--- a/dom/base/nsIContent.h
+++ b/dom/base/nsIContent.h
@@ -75,9 +75,12 @@ class nsIContent : public nsINode {
 
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_ICONTENT_IID)
 
-  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS_FINAL_DELETECYCLECOLLECTABLE
+
   NS_DECL_CYCLE_COLLECTION_CLASS(nsIContent)
 
+  NS_DECL_DOMARENA_DESTROY
+
   NS_IMPL_FROMNODE_HELPER(nsIContent, IsContent())
 
   /**
diff --git a/xpcom/base/nsISupportsImpl.h b/xpcom/base/nsISupportsImpl.h
index 1264066200ad..6b32fdf1a61e 100644
--- a/xpcom/base/nsISupportsImpl.h
+++ b/xpcom/base/nsISupportsImpl.h
@@ -936,6 +936,31 @@ class ThreadSafeAutoRefCnt {
   }                                                                                        \
   NS_IMETHODIMP_(void) _class::DeleteCycleCollectable(void) { delete this; }
 
+// _LAST_RELEASE can be useful when certain resources should be released
+// as soon as we know the object will be deleted.
+#define NS_IMPL_MAIN_THREAD_ONLY_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE_AND_DESTROY( \
+    _class, _last, _destroy)                                                             \
+  NS_IMETHODIMP_(MozExternalRefCountType) _class::Release(void) {                        \
+    MOZ_ASSERT(int32_t(mRefCnt) > 0, "dup release");                                     \
+    NS_ASSERT_OWNINGTHREAD(_class);                                                      \
+    bool shouldDelete = false;                                                           \
+    nsISupports* base = NS_CYCLE_COLLECTION_CLASSNAME(_class)::Upcast(this);             \
+    nsrefcnt count = mRefCnt.decr<NS_CycleCollectorSuspectUsingNursery>(                 \
+        base, &shouldDelete);                                                            \
+    NS_LOG_RELEASE(this, count, #_class);                                                \
+    if (count == 0) {                                                                    \
+      mRefCnt.incr<NS_CycleCollectorSuspectUsingNursery>(base);                          \
+      _last;                                                                             \
+      mRefCnt.decr<NS_CycleCollectorSuspectUsingNursery>(base);                          \
+      if (shouldDelete) {                                                                \
+        mRefCnt.stabilizeForDeletion();                                                  \
+        DeleteCycleCollectable();                                                        \
+      }                                                                                  \
+    }                                                                                    \
+    return count;                                                                        \
+  }                                                                                      \
+  NS_IMETHODIMP_(void) _class::DeleteCycleCollectable(void) { _destroy; }
+
 ///////////////////////////////////////////////////////////////////////////////
 
 /**