Move lazy event dispatching code out of EventRouter.

extensions/browser/lazy_context_id.cc

Index: extensions/browser/lazy_context_id.cc
diff --git a/extensions/browser/lazy_context_id.cc b/extensions/browser/lazy_context_id.cc
new file mode 100644
index 0000000000000000000000000000000000000000..80a4dcfacfeaa71db2283cdb2ff1d8cd8df4e5e4
--- /dev/null
+++ b/extensions/browser/lazy_context_id.cc
@@ -0,0 +1,20 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "extensions/browser/lazy_context_id.h"
+
+#include "extensions/browser/lazy_background_task_queue.h"
+
+namespace extensions {
+
+LazyContextId::LazyContextId(content::BrowserContext* context,
+                             const ExtensionId& extension_id)
+    : type_(Type::kEventPage), context_(context), extension_id_(extension_id) {}
+
+LazyBackgroundTaskQueue* LazyContextId::GetTaskQueue() {
+  DCHECK(is_for_event_page());
+  return LazyBackgroundTaskQueue::Get(context_);
+}
+
+}  // namespace extensions