Bug 1332494 - Add SystemGroup class similar to TabGroup/DocGroup (r=froydnj)

MozReview-Commit-ID: ApxMkd5zEQ5

xpcom/threads/SystemGroup.cpp

@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SystemGroup.h"
+
+#include "mozilla/Move.h"
+#include "nsINamed.h"
+
+using namespace mozilla;
+
+/* static */ nsresult
+SystemGroup::Dispatch(const char* aName,
+                      TaskCategory aCategory,
+                      already_AddRefed<nsIRunnable>&& aRunnable)
+{
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  if (aName) {
+    if (nsCOMPtr<nsINamed> named = do_QueryInterface(runnable)) {
+      named->SetName(aName);
+    }
+  }
+  if (NS_IsMainThread()) {
+    return NS_DispatchToCurrentThread(runnable.forget());
+  } else {
+    return NS_DispatchToMainThread(runnable.forget());
+  }
+}
+
+/* static */ nsIEventTarget*
+SystemGroup::EventTargetFor(TaskCategory aCategory)
+{
+  nsCOMPtr<nsIEventTarget> main = do_GetMainThread();
+  return main;
+}
+

xpcom/threads/SystemGroup.h

@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_SystemGroup_h
+#define mozilla_SystemGroup_h
+
+#include "mozilla/TaskCategory.h"
+
+// The SystemGroup should be used for dispatching runnables that don't need to
+// touch web content. Runnables dispatched to the SystemGroup are run in order
+// relative to each other, but their order relative to other runnables is
+// undefined.
+
+namespace mozilla {
+
+class SystemGroup {
+ public:
+  // This method is safe to use from any thread.
+  static nsresult Dispatch(const char* aName,
+                           TaskCategory aCategory,
+                           already_AddRefed<nsIRunnable>&& aRunnable);
+
+  // This method is safe to use from any thread.
+  static nsIEventTarget* EventTargetFor(TaskCategory aCategory);
+};
+
+} // namespace mozilla
+
+#endif // mozilla_SystemGroup_h
+

xpcom/threads/moz.build

@@ -51,6 +51,7 @@ EXPORTS.mozilla += [
     'StateMirroring.h',
     'StateWatching.h',
     'SyncRunnable.h',
+    'SystemGroup.h',
     'TaskCategory.h',
     'TaskDispatcher.h',
     'TaskQueue.h',
@@ -76,6 +77,7 @@ UNIFIED_SOURCES += [
     'nsThreadUtils.cpp',
     'nsTimerImpl.cpp',
     'SharedThreadPool.cpp',
+    'SystemGroup.cpp',
     'TaskQueue.cpp',
     'ThreadStackHelper.cpp',
     'ThrottledEventQueue.cpp',