Move lazy event dispatching code out of EventRouter.

extensions/browser/events/lazy_event_dispatcher.h

+// 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.
+
+#ifndef EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCHER_H_
+#define EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCHER_H_
+
+#include <set>
+#include <utility>
+
+#include "base/callback.h"
+#include "base/memory/linked_ptr.h"
+#include "extensions/common/extension_id.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace content {
+class BrowserContext;
+}
+
+namespace extensions {
+class EventListener;
+class Extension;
+class ExtensionHost;
+class LazyContextId;
+struct Event;
+
+// Helper class for EventRouter to dispatch lazy events to lazy contexts.
+//
+// Manages waking up lazy contexts if they are stopped.
+class LazyEventDispatcher {
+ public:
+  // TODO(lazyboy): ExtensionHost is specific to events pages, provide a generic
+  // context info that works for both event pages and service workers.
+  using DispatchFunc =

[Devlin, 2017/06/15 01:37:26]

nit: s/Func/Function (avoid less common abbreviations)

[lazyboy, 2017/06/15 04:39:22]

Done.

+      base::Callback<void(const linked_ptr<Event>&, ExtensionHost*)>;
+
+  LazyEventDispatcher(content::BrowserContext* browser_context,
+                      const linked_ptr<Event>& event,
+                      const DispatchFunc& dispatch_func);
+  ~LazyEventDispatcher();
+
+  // Dispatches a lazy event to |extension_id|.
+  //
+  // Ensures that all lazy background pages that are interested in the given
+  // event are loaded, and queues the event if the page is not ready yet.
+  void DispatchToEventPage(const ExtensionId& extension_id,
+                           const base::DictionaryValue* listener_filter);
+
+  // Returns whether or not a listener is queued for dispatch already.

[Devlin, 2017/06/15 01:37:26]

nit: maybe s/a listener/an identical listener?

[lazyboy, 2017/06/15 04:39:22]

Done.

+  bool HasAlreadyDispatched(content::BrowserContext* context,
+                            const EventListener* listener) const;
+
+ private:
+  using EventPageDispatchIdentifier =
+      std::pair<const content::BrowserContext*, std::string>;
+
+  void DispatchToLazyContext(LazyContextId* dispatch_context,
+                             const base::DictionaryValue* listener_filter);

[Devlin, 2017/06/15 01:37:26]

nit: \n

[lazyboy, 2017/06/15 04:39:22]

Done.

+  // Possibly loads given extension's background page or extension Service
+  // Worker in preparation to dispatch an event.  Returns true if the event was
+  // queued for subsequent dispatch, false otherwise.
+  bool QueueEventDispatch(LazyContextId* dispatch_context,
+                          const Extension* extension,
+                          const base::DictionaryValue* listener_filter);

[Devlin, 2017/06/15 01:37:26]

nit: \n (after the other functions, too)

[lazyboy, 2017/06/15 04:39:22]

Done.

+  bool HasAlreadyDispatchedImpl(const LazyContextId* dispatch_context) const;
+  void RecordAlreadyDispatched(LazyContextId* dispatch_context);
+  content::BrowserContext* GetIncognitoContext(const Extension* extension);
+
+  content::BrowserContext* const browser_context_;
+  linked_ptr<Event> event_;
+  DispatchFunc dispatch_func_;
+
+  std::set<EventPageDispatchIdentifier> dispatched_ep_ids_;

[Devlin, 2017/06/15 01:37:26]

s/ep/<something else - or nothing.  dispatched_ids_ is probably fine>

[lazyboy, 2017/06/15 04:39:22]

I want something other than plain dispatch_ids_ b/c I'll need to add another set
for service workers and I want to differentiate between the two clearly.

I'll just name it (verbose) dispatched_ids_for_event_page_;

+
+  DISALLOW_COPY_AND_ASSIGN(LazyEventDispatcher);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCHER_H_