Bug 1241763: Don't fire dom-window-destroyed on outer windows. r=bz

dom/base/nsGlobalWindow.cpp

@@ -1622,6 +1622,9 @@ nsGlobalWindow::FreeInnerObjects()
   // other members that the window destroyed observers could
   // re-create.
   NotifyDOMWindowDestroyed(this);
+  if (auto* reporter = nsWindowMemoryReporter::Get()) {
+    reporter->ObserveDOMWindowDetached(this);
+  }
 
   mInnerObjectsFreed = true;
 
@@ -2932,8 +2935,9 @@ nsGlobalWindow::DetachFromDocShell()
     inner->FreeInnerObjects();
   }
 
-  // Make sure that this is called before we null out the document.
-  NotifyDOMWindowDestroyed(this);
+  if (auto* reporter = nsWindowMemoryReporter::Get()) {
+    reporter->ObserveDOMWindowDetached(this);
+  }
 
   NotifyWindowIDDestroyed("outer-window-destroyed");
 

dom/base/nsPIDOMWindow.h

@@ -17,6 +17,7 @@
 #include "js/TypeDecls.h"
 #include "nsRefPtrHashtable.h"
 
+// Only fired for inner windows.
 #define DOM_WINDOW_DESTROYED_TOPIC "dom-window-destroyed"
 #define DOM_WINDOW_FROZEN_TOPIC "dom-window-frozen"
 #define DOM_WINDOW_THAWED_TOPIC "dom-window-thawed"

dom/base/nsWindowMemoryReporter.cpp

@@ -111,10 +111,6 @@ nsWindowMemoryReporter::Init()
 
   nsCOMPtr<nsIObserverService> os = services::GetObserverService();
   if (os) {
-    // DOM_WINDOW_DESTROYED_TOPIC announces what we call window "detachment",
-    // when a window's docshell is set to nullptr.
-    os->AddObserver(sWindowReporter, DOM_WINDOW_DESTROYED_TOPIC,
-                    /* weakRef = */ true);
     os->AddObserver(sWindowReporter, "after-minimize-memory-usage",
                     /* weakRef = */ true);
     os->AddObserver(sWindowReporter, "cycle-collector-begin",
@@ -127,6 +123,12 @@ nsWindowMemoryReporter::Init()
   RegisterGhostWindowsDistinguishedAmount(GhostWindowsReporter::DistinguishedAmount);
 }
 
+/* static */ nsWindowMemoryReporter*
+nsWindowMemoryReporter::Get()
+{
+  return sWindowReporter;
+}
+
 static already_AddRefed<nsIURI>
 GetWindowURI(nsIDOMWindow *aWindow)
 {
@@ -614,9 +616,7 @@ NS_IMETHODIMP
 nsWindowMemoryReporter::Observe(nsISupports *aSubject, const char *aTopic,
                                 const char16_t *aData)
 {
-  if (!strcmp(aTopic, DOM_WINDOW_DESTROYED_TOPIC)) {
-    ObserveDOMWindowDetached(aSubject);
-  } else if (!strcmp(aTopic, "after-minimize-memory-usage")) {
+  if (!strcmp(aTopic, "after-minimize-memory-usage")) {
     ObserveAfterMinimizeMemoryUsage();
   } else if (!strcmp(aTopic, "cycle-collector-begin")) {
     if (mCheckTimer) {
@@ -638,9 +638,9 @@ nsWindowMemoryReporter::Observe(nsISupports *aSubject, const char *aTopic,
 }
 
 void
-nsWindowMemoryReporter::ObserveDOMWindowDetached(nsISupports* aWindow)
+nsWindowMemoryReporter::ObserveDOMWindowDetached(nsGlobalWindow* aWindow)
 {
-  nsWeakPtr weakWindow = do_GetWeakReference(aWindow);
+  nsWeakPtr weakWindow = do_GetWeakReference(static_cast<nsIDOMEventTarget*>(aWindow));
   if (!weakWindow) {
     NS_WARNING("Couldn't take weak reference to a window?");
     return;

dom/base/nsWindowMemoryReporter.h

@@ -158,6 +158,9 @@ public:
   static void UnlinkGhostWindows();
 #endif
 
+  static nsWindowMemoryReporter* Get();
+  void ObserveDOMWindowDetached(nsGlobalWindow* aWindow);
+
 private:
   ~nsWindowMemoryReporter();
 
@@ -199,7 +202,6 @@ private:
    */
   uint32_t GetGhostTimeout();
 
-  void ObserveDOMWindowDetached(nsISupports* aWindow);
   void ObserveAfterMinimizeMemoryUsage();
 
   /**