Bug 399107: Add API to force cycle collection. r/sr/a=jst

dom/public/idl/base/nsIDOMWindowUtils.idl

@@ -47,7 +47,7 @@
 
 interface nsIDOMElement;
 
-[scriptable, uuid(25f55fb2-a6f8-4f7f-93c3-3adafd5166bc)]
+[scriptable, uuid(7a55fc2b-afb3-41c6-9e50-3fee341fa87c)]
 interface nsIDOMWindowUtils : nsISupports {
 
   /**
@@ -156,4 +156,13 @@ interface nsIDOMWindowUtils : nsISupports {
    * @param aElement the element to focus
    */
   void focus(in nsIDOMElement aElement);
+
+  /**
+   * Force a garbage collection. This will run the cycle-collector twice to
+   * make sure all garbage is collected.
+   *
+   * Will throw a DOM security error if called without UniversalXPConnect
+   * privileges in non-debug builds. Available to all callers in debug builds.
+   */
+  void garbageCollect();
 };

dom/src/base/nsDOMWindowUtils.cpp

@@ -53,6 +53,7 @@
 #include "nsIWidget.h"
 #include "nsGUIEvent.h"
 #include "nsIParser.h"
+#include "nsCycleCollector.h"
 
 #ifdef MOZ_ENABLE_GTK2
 #include <gdk/gdkx.h>
@@ -327,3 +328,21 @@ nsDOMWindowUtils::Focus(nsIDOMElement* aElement)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::GarbageCollect()
+{
+  // NOTE: Only do this in NON debug builds, as this function can useful
+  // during debugging.
+#ifndef DEBUG
+  PRBool hasCap = PR_FALSE;
+  if (NS_FAILED(nsContentUtils::GetSecurityManager()->
+                  IsCapabilityEnabled("UniversalXPConnect", &hasCap))
+      || !hasCap)
+    return NS_ERROR_DOM_SECURITY_ERR;
+#endif
+
+  nsCycleCollector_collect();
+  nsCycleCollector_collect();
+
+  return NS_OK;
+}