bug 1171785 create nsContentUtils::RunInStableState helper r=bholley

dom/base/nsContentUtils.cpp

@@ -92,6 +92,7 @@
 #include "nsHostObjectProtocolHandler.h"
 #include "nsHtml5Module.h"
 #include "nsHtml5StringParser.h"
+#include "nsIAppShell.h"
 #include "nsIAsyncVerifyRedirectCallback.h"
 #include "nsICategoryManager.h"
 #include "nsIChannelEventSink.h"
@@ -182,6 +183,7 @@
 #include "nsUnicodeProperties.h"
 #include "nsViewManager.h"
 #include "nsViewportInfo.h"
+#include "nsWidgetsCID.h"
 #include "nsWrapperCacheInlines.h"
 #include "nsXULPopupManager.h"
 #include "xpcprivate.h" // nsXPConnect
@@ -337,6 +339,7 @@ namespace {
 
 static NS_DEFINE_CID(kParserServiceCID, NS_PARSERSERVICE_CID);
 static NS_DEFINE_CID(kCParserCID, NS_PARSER_CID);
+static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
 
 static PLDHashTable* sEventListenerManagersHash;
 
@@ -5148,6 +5151,22 @@ nsContentUtils::AddScriptRunner(nsIRunnable* aRunnable)
   return true;
 }
 
+/* static */
+void
+nsContentUtils::RunInStableState(already_AddRefed<nsIRunnable> aRunnable,
+                                 DispatchFailureHandling aHandling)
+{
+  nsCOMPtr<nsIRunnable> runnable = aRunnable;
+  nsCOMPtr<nsIAppShell> appShell(do_GetService(kAppShellCID));
+  if (!appShell) {
+    MOZ_ASSERT(aHandling == DispatchFailureHandling::IgnoreFailure);
+    return;
+  }
+  DebugOnly<nsresult> rv = appShell->RunInStableState(runnable);
+  MOZ_ASSERT(NS_SUCCEEDED(rv) ||
+             aHandling == DispatchFailureHandling::IgnoreFailure);
+}
+
 void
 nsContentUtils::EnterMicroTask()
 {

dom/base/nsContentUtils.h

@@ -1576,6 +1576,27 @@ public:
    */
   static void WarnScriptWasIgnored(nsIDocument* aDocument);
 
+  /**
+   * Whether to assert that RunInStableState() succeeds, or ignore failure,
+   * which may happen late in shutdown.
+   */
+  enum class DispatchFailureHandling { AssertSuccess, IgnoreFailure };
+
+  /**
+   * Add a "synchronous section", in the form of an nsIRunnable run once the
+   * event loop has reached a "stable state". |aRunnable| must not cause any
+   * queued events to be processed (i.e. must not spin the event loop).
+   * We've reached a stable state when the currently executing task/event has
+   * finished, see
+   * http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#synchronous-section
+   * In practice this runs aRunnable once the currently executing event
+   * finishes. If called multiple times per task/event, all the runnables will
+   * be executed, in the order in which RunInStableState() was called.
+   */
+  static void RunInStableState(already_AddRefed<nsIRunnable> aRunnable,
+                               DispatchFailureHandling aHandling =
+                                 DispatchFailureHandling::AssertSuccess);
+
   /**
    * Retrieve information about the viewport as a data structure.
    * This will return information in the viewport META data section