Create interface "EventPageTracker" for checking an extension's

extensions/browser/process_manager.cc

Index: extensions/browser/process_manager.cc
diff --git a/extensions/browser/process_manager.cc b/extensions/browser/process_manager.cc
index 47f7b191e004da8dccf2a6179c9a17a73471752f..8f11eae63cf139782cc10ede9960b22baabb6f17 100644
--- a/extensions/browser/process_manager.cc
+++ b/extensions/browser/process_manager.cc
@@ -23,6 +23,7 @@
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extensions_browser_client.h"
+#include "extensions/browser/lazy_background_task_queue.h"
 #include "extensions/browser/notification_types.h"
 #include "extensions/browser/process_manager_delegate.h"
 #include "extensions/browser/process_manager_factory.h"
@@ -107,6 +108,11 @@ static void CreateBackgroundHostForExtensionLoad(
                                   BackgroundInfo::GetBackgroundURL(extension));
 }
 
+void OnExtensionLoad(const base::Callback<void(bool)>& callback,
+                     extensions::ExtensionHost* host) {
+  callback.Run(host != nullptr);
+}
+
 }  // namespace
 
 struct ProcessManager::BackgroundPageData {
@@ -406,6 +412,18 @@ ExtensionHost* ProcessManager::GetBackgroundHostForExtension(
   return nullptr;
 }
 
+void ProcessManager::WakeExtension(const std::string& extension_id,
+                                   const base::Callback<void(bool)>& callback) {
+  if (GetBackgroundHostForExtension(extension_id)) {
+    // Run the callback immediately if the extension is already awake.
+    callback.Run(true);

[not at google - send to devlin, 2015/04/24 20:05:08]

Re-entrant callbacks lead to insidious bugs. Either post to the current message
loop, or signal to caller via a bool return value if already active (and don't
call the callback in that case).

[Kevin Marshall, 2015/04/24 21:04:53]

Good point, using return value. Updated docs.

+  }
+  LazyBackgroundTaskQueue* queue =
+      ExtensionSystem::Get(browser_context_)->lazy_background_task_queue();
+  queue->AddPendingTask(browser_context_, extension_id,
+                        base::Bind(&OnExtensionLoad, callback));

[not at google - send to devlin, 2015/04/24 20:05:08]

Is there a better / more descriptive name than just "OnExtensionLoad"?

[Kevin Marshall, 2015/04/24 21:04:53]

How's this? "PropagateExtensionWakeResult"

+}
+
 bool ProcessManager::IsBackgroundHostClosing(const std::string& extension_id) {
   ExtensionHost* host = GetBackgroundHostForExtension(extension_id);
   return (host && background_page_data_[extension_id].is_closing);