Reland: Refactor code that defers extension background page loading

extensions/browser/process_manager.h

Index: extensions/browser/process_manager.h
diff --git a/extensions/browser/process_manager.h b/extensions/browser/process_manager.h
index e580bbd9335205b8b22ec164c25930d9e9853802..80736e4844b33e7f830a6834b27f6fab0345ef27 100644
--- a/extensions/browser/process_manager.h
+++ b/extensions/browser/process_manager.h
@@ -33,6 +33,7 @@ namespace extensions {
 
 class Extension;
 class ExtensionHost;
+class ProcessManagerDelegate;
 class ProcessManagerObserver;
 
 // Manages dynamic state of running Chromium extensions. There is one instance
@@ -122,8 +123,9 @@ class ProcessManager : public content::NotificationObserver {
   // onSuspendCanceled() event to it.
   void CancelSuspend(const Extension* extension);
 
-  // Ensures background hosts are loaded for a new browser window.
-  void OnBrowserWindowReady();
+  // Creates background hosts if the embedder is ready and they are not already
+  // loaded.
+  void MaybeCreateStartupBackgroundHosts();
 
   // Gets the BrowserContext associated with site_instance_ and all other
   // related SiteInstances.
@@ -144,6 +146,10 @@ class ProcessManager : public content::NotificationObserver {
       content::BrowserContext* original_context,
       ProcessManager* original_manager);
 
+  bool startup_background_hosts_created_for_test() const {
+    return startup_background_hosts_created_;
+  }
+
  protected:
   // If |context| is incognito pass the master context as |original_context|.
   // Otherwise pass the same context for both.
@@ -158,10 +164,6 @@ class ProcessManager : public content::NotificationObserver {
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
-  // Load all background pages once the profile data is ready and the pages
-  // should be loaded.
-  void CreateBackgroundHostsForProfileStartup();
-
   content::NotificationRegistrar registrar_;
 
   // The set of ExtensionHosts running viewless background extensions.
@@ -182,6 +184,10 @@ class ProcessManager : public content::NotificationObserver {
   typedef std::map<content::RenderViewHost*,
       extensions::ViewType> ExtensionRenderViews;
 
+  // Load all background pages once the profile data is ready and the pages
+  // should be loaded.
+  void CreateStartupBackgroundHosts();
+
   // Called just after |host| is created so it can be registered in our lists.
   void OnBackgroundHostCreated(ExtensionHost* host);
 
@@ -216,9 +222,6 @@ class ProcessManager : public content::NotificationObserver {
   // Clears background page data for this extension.
   void ClearBackgroundPageData(const std::string& extension_id);
 
-  // Returns true if loading background pages should be deferred.
-  bool DeferLoadingBackgroundHosts() const;
-
   void OnDevToolsStateChanged(content::DevToolsAgentHost*, bool attached);
 
   // Contains all active extension-related RenderViewHost instances for all