Lazy creation of background pages with --enable-lazy-background-pages

BUG=81752
TEST=None


Review URL: http://codereview.chromium.org/7672009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98981 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 195 insertions, 50 deletions

diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index f5558d9..96bb3df 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4324,6 +4324,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_CRXLESS_WEB_APPS_DESCRIPTION" desc="Description of the CRX-less web apps lab">
         Enables support for installing Chrome apps that are deployed using a manifest file on a webpage, rather than by packaging the manifest and icons into a crx file.
       </message>
+      <message name="IDS_FLAGS_LAZY_BACKGROUND_PAGES_NAME" desc="Title of the flag to enable lazy loading of extension background pages.">
+        Lazy Background Pages
+      </message>
+      <message name="IDS_FLAGS_LAZY_BACKGROUND_PAGES_DESCRIPTION" desc="Description of the flag to enable lazy loading of extension background pages.">
+        Enables some extension background pages to be loaded when they are needed rather than when the extensions are first loaded.
+      </message>
       <message name="IDS_FLAGS_CONFLICTS_CHECK_NAME" desc="Title of the run conflicts check flag">
         Check for known conflicts with 3rd party modules.
       </message>
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 263f031..60b325d 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -126,6 +126,13 @@ const Experiment kExperiments[] = {
     SINGLE_VALUE_TYPE(switches::kEnableCrxlessWebApps)
   },
   {
+    "lazy-background-pages",
+    IDS_FLAGS_LAZY_BACKGROUND_PAGES_NAME,
+    IDS_FLAGS_LAZY_BACKGROUND_PAGES_DESCRIPTION,
+    kOsAll,
+    SINGLE_VALUE_TYPE(switches::kEnableLazyBackgroundPages)
+  },
+  {
     "ignore-gpu-blacklist",
     IDS_FLAGS_IGNORE_GPU_BLACKLIST_NAME,
     IDS_FLAGS_IGNORE_GPU_BLACKLIST_DESCRIPTION,
diff --git a/chrome/browser/extensions/extension_event_router.cc b/chrome/browser/extensions/extension_event_router.cc
index 7a9cb340..eb458c8 100644
--- a/chrome/browser/extensions/extension_event_router.cc
+++ b/chrome/browser/extensions/extension_event_router.cc
@@ -4,14 +4,17 @@
 
 #include "chrome/browser/extensions/extension_event_router.h"
 
+#include "base/command_line.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/extension_devtools_manager.h"
+#include "chrome/browser/extensions/extension_host.h"
 #include "chrome/browser/extensions/extension_processes_api.h"
 #include "chrome/browser/extensions/extension_processes_api_constants.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_tabs_module.h"
 #include "chrome/browser/extensions/extension_webrequest_api.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "content/browser/child_process_security_policy.h"
@@ -48,6 +51,28 @@ struct ExtensionEventRouter::EventListener {
   }
 };
 
+struct ExtensionEventRouter::ExtensionEvent {
+  std::string extension_id;
+  std::string event_name;
+  std::string event_args;
+  GURL event_url;
+  Profile* restrict_to_profile;
+  std::string cross_incognito_args;
+
+  ExtensionEvent(const std::string& extension_id,
+                 const std::string& event_name,
+                 const std::string& event_args,
+                 const GURL& event_url,
+                 Profile* restrict_to_profile,
+                 const std::string& cross_incognito_args)
+    : extension_id(extension_id),
+      event_name(event_name),
+      event_args(event_args),
+      event_url(event_url),
+      restrict_to_profile(restrict_to_profile),
+      cross_incognito_args(cross_incognito_args) {}
+};
+
 // static
 void ExtensionEventRouter::DispatchEvent(IPC::Message::Sender* ipc_sender,
                                          const std::string& extension_id,
@@ -68,10 +93,12 @@ ExtensionEventRouter::ExtensionEventRouter(Profile* profile)
                  NotificationService::AllSources());
   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
                  NotificationService::AllSources());
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_HOST_DID_STOP_LOADING,
+                 Source<Profile>(profile_));
+  // TODO(tessamac): also get notified for background page crash/failure.
 }
 
-ExtensionEventRouter::~ExtensionEventRouter() {
-}
+ExtensionEventRouter::~ExtensionEventRouter() {}
 
 void ExtensionEventRouter::AddEventListener(
     const std::string& event_name,
@@ -142,8 +169,10 @@ void ExtensionEventRouter::DispatchEventToRenderers(
     const std::string& event_args,
     Profile* restrict_to_profile,
     const GURL& event_url) {
-  DispatchEventImpl("", event_name, event_args, restrict_to_profile, "",
-                    event_url);
+  linked_ptr<ExtensionEvent> event(
+      new ExtensionEvent("", event_name, event_args, event_url,
+                         restrict_to_profile, ""));
+  DispatchEventImpl(event, false);
 }
 
 void ExtensionEventRouter::DispatchEventToExtension(
@@ -153,8 +182,10 @@ void ExtensionEventRouter::DispatchEventToExtension(
     Profile* restrict_to_profile,
     const GURL& event_url) {
   DCHECK(!extension_id.empty());
-  DispatchEventImpl(extension_id, event_name, event_args, restrict_to_profile,
-                    "", event_url);
+  linked_ptr<ExtensionEvent> event(
+      new ExtensionEvent(extension_id, event_name, event_args, event_url,
+                         restrict_to_profile, ""));
+  DispatchEventImpl(event, false);
 }
 
 void ExtensionEventRouter::DispatchEventsToRenderersAcrossIncognito(
@@ -163,24 +194,56 @@ void ExtensionEventRouter::DispatchEventsToRenderersAcrossIncognito(
     Profile* restrict_to_profile,
     const std::string& cross_incognito_args,
     const GURL& event_url) {
-  DispatchEventImpl("", event_name, event_args, restrict_to_profile,
-                    cross_incognito_args, event_url);
+  linked_ptr<ExtensionEvent> event(
+      new ExtensionEvent("", event_name, event_args, event_url,
+                         restrict_to_profile, cross_incognito_args));
+  DispatchEventImpl(event, false);
+}
+
+bool ExtensionEventRouter::CanDispatchEventNow(
+    const std::string& extension_id) {
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableLazyBackgroundPages))
+    return true;
+
+  if (extension_id.empty())
+    // TODO(tessamac): Create all background pages. Wait for all to be loaded?
+    //                 or dispatch event to each extension when it's ready?
+    return true;
+
+  const Extension* extension = profile_->GetExtensionService()->
+      GetExtensionById(extension_id, false);  // exclude disabled extensions
+  if (extension && extension->background_url().is_valid()) {
+    ExtensionProcessManager* pm = profile_->GetExtensionProcessManager();
+    if (!pm->GetBackgroundHostForExtension(extension)) {
+      pm->CreateBackgroundHost(extension, extension->background_url());
+      return false;
+    }
+  }
+
+  return true;
 }
 
 void ExtensionEventRouter::DispatchEventImpl(
-    const std::string& extension_id,
-    const std::string& event_name,
-    const std::string& event_args,
-    Profile* restrict_to_profile,
-    const std::string& cross_incognito_args,
-    const GURL& event_url) {
+    const linked_ptr<ExtensionEvent>& event, bool was_pending) {
   if (!profile_)
     return;
 
   // We don't expect to get events from a completely different profile.
-  DCHECK(!restrict_to_profile || profile_->IsSameProfile(restrict_to_profile));
+  DCHECK(!event->restrict_to_profile ||
+         profile_->IsSameProfile(event->restrict_to_profile));
+
+  if (!CanDispatchEventNow(event->extension_id)) {
+    // Events should not be made pending twice. This may happen if the
+    // background page is shutdown before we finish dispatching pending events.
+    CHECK(!was_pending);
+    // TODO(tessamac): make sure Background Page notification doesn't
+    //                 happen before the event is added to the pending list.
+    AppendEvent(event);
+    return;
+  }
 
-  ListenerMap::iterator it = listeners_.find(event_name);
+  ListenerMap::iterator it = listeners_.find(event->event_name);
   if (it == listeners_.end())
     return;
 
@@ -196,30 +259,66 @@ void ExtensionEventRouter::DispatchEventImpl(
       continue;
     }
 
-    if (!extension_id.empty() && extension_id != listener->extension_id)
+    if (!event->extension_id.empty() &&
+        event->extension_id != listener->extension_id)
       continue;
 
     // Is this event from a different profile than the renderer (ie, an
     // incognito tab event sent to a normal process, or vice versa).
-    bool cross_incognito = restrict_to_profile &&
-        listener->process->browser_context() != restrict_to_profile;
+    bool cross_incognito = event->restrict_to_profile &&
+        listener->process->browser_context() != event->restrict_to_profile;
     const Extension* extension = service->GetExtensionById(
         listener->extension_id, false);
     // Send the event with different arguments to extensions that can't
     // cross incognito, if necessary.
     if (cross_incognito && !service->CanCrossIncognito(extension)) {
-      if (!cross_incognito_args.empty()) {
+      if (!event->cross_incognito_args.empty()) {
         DispatchEvent(listener->process, listener->extension_id,
-                      event_name, cross_incognito_args, event_url);
+                      event->event_name, event->cross_incognito_args,
+                      event->event_url);
       }
       continue;
     }
 
     DispatchEvent(listener->process, listener->extension_id,
-                  event_name, event_args, event_url);
+                  event->event_name, event->event_args, event->event_url);
   }
 }
 
+void ExtensionEventRouter::AppendEvent(
+    const linked_ptr<ExtensionEvent>& event) {
+  PendingEventsList* events_list = NULL;
+  PendingEventsPerExtMap::iterator it =
+      pending_events_.find(event->extension_id);
+  if (it == pending_events_.end()) {
+    events_list = new PendingEventsList();
+    pending_events_[event->extension_id] =
+        linked_ptr<PendingEventsList>(events_list);
+  } else {
+    events_list = it->second.get();
+  }
+
+  events_list->push_back(event);
+}
+
+void ExtensionEventRouter::DispatchPendingEvents(
+    const std::string &extension_id) {
+  // Find the list of pending events for this extension.
+  PendingEventsPerExtMap::const_iterator map_it =
+      pending_events_.find(extension_id);
+  if (map_it == pending_events_.end())
+    return;
+
+  PendingEventsList* events_list = map_it->second.get();
+  for (PendingEventsList::const_iterator it = events_list->begin();
+       it != events_list->end(); ++it)
+    DispatchEventImpl(*it, true);
+
+  // Delete list.
+  events_list->clear();
+  pending_events_.erase(extension_id);
+}
+
 void ExtensionEventRouter::Observe(int type,
                                    const NotificationSource& source,
                                    const NotificationDetails& details) {
@@ -243,6 +342,13 @@ void ExtensionEventRouter::Observe(int type,
       }
       break;
     }
+    case chrome::NOTIFICATION_EXTENSION_HOST_DID_STOP_LOADING: {
+      // TODO: dispatch events in queue.  ExtensionHost is in the details.
+      ExtensionHost* eh = Details<ExtensionHost>(details).ptr();
+      DispatchPendingEvents(eh->extension_id());
+      break;
+    }
+    // TODO(tessamac): if background page crashed/failed clear queue.
     default:
       NOTREACHED();
       return;
diff --git a/chrome/browser/extensions/extension_event_router.h b/chrome/browser/extensions/extension_event_router.h
index d46e05f..99ca416 100644
--- a/chrome/browser/extensions/extension_event_router.h
+++ b/chrome/browser/extensions/extension_event_router.h
@@ -10,6 +10,7 @@
 #include <set>
 #include <string>
 
+#include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "content/common/notification_observer.h"
 #include "content/common/notification_registrar.h"
@@ -65,7 +66,7 @@ class ExtensionEventRouter : public NotificationObserver {
       const GURL& event_url);
 
   // Same as above, except only send the event to the given extension.
-  void DispatchEventToExtension(
+  virtual void DispatchEventToExtension(
       const std::string& extension_id,
       const std::string& event_name,
       const std::string& event_args,
@@ -87,15 +88,22 @@ class ExtensionEventRouter : public NotificationObserver {
       const GURL& event_url);
 
  protected:
+  // The details of an event to be dispatched.
+  struct ExtensionEvent;
+
   // Shared by DispatchEvent*. If |extension_id| is empty, the event is
   // broadcast.
-  virtual void DispatchEventImpl(
-      const std::string& extension_id,
-      const std::string& event_name,
-      const std::string& event_args,
-      Profile* restrict_to_profile,
-      const std::string& cross_incognito_args,
-      const GURL& event_url);
+  // An event that just came off the pending list may not be delayed again.
+  void DispatchEventImpl(const linked_ptr<ExtensionEvent>& event,
+                         bool was_pending);
+
+  // Dispatch may be delayed if the extension has a lazy background page.
+  bool CanDispatchEventNow(const std::string& extension_id);
+
+  // Store the event so that it can be dispatched (in order received)
+  // when the background page is done loading.
+  void AppendEvent(const linked_ptr<ExtensionEvent>& event);
+  void DispatchPendingEvents(const std::string& extension_id);
 
  private:
   // An extension listening to an event.
@@ -116,6 +124,13 @@ class ExtensionEventRouter : public NotificationObserver {
   typedef std::map<std::string, std::set<EventListener> > ListenerMap;
   ListenerMap listeners_;
 
+  // A map between an extension id and the queue of events pending
+  // the load of it's background page.
+  typedef std::vector<linked_ptr<ExtensionEvent> > PendingEventsList;
+  typedef std::map<std::string,
+                   linked_ptr<PendingEventsList> > PendingEventsPerExtMap;
+  PendingEventsPerExtMap pending_events_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionEventRouter);
 };
 
diff --git a/chrome/browser/extensions/extension_menu_manager_unittest.cc b/chrome/browser/extensions/extension_menu_manager_unittest.cc
index bb834cb..eef1afd 100644
--- a/chrome/browser/extensions/extension_menu_manager_unittest.cc
+++ b/chrome/browser/extensions/extension_menu_manager_unittest.cc
@@ -347,12 +347,12 @@ class MockExtensionEventRouter : public ExtensionEventRouter {
   explicit MockExtensionEventRouter(Profile* profile) :
       ExtensionEventRouter(profile) {}
 
-  MOCK_METHOD6(DispatchEventImpl, void(const std::string& extension_id,
-                                       const std::string& event_name,
-                                       const std::string& event_args,
-                                       Profile* source_profile,
-                                       const std::string& cross_incognito_args,
-                                       const GURL& event_url));
+  MOCK_METHOD5(DispatchEventToExtension, void(const std::string& extension_id,
+                                              const std::string& event_name,
+                                              const std::string& event_args,
+                                              Profile* source_profile,
+                                              const GURL& event_url));
+
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MockExtensionEventRouter);
@@ -445,12 +445,11 @@ TEST_F(ExtensionMenuManagerTest, ExecuteCommand) {
   std::string event_args;
   std::string expected_event_name = "contextMenus";
   EXPECT_CALL(*mock_event_router.get(),
-              DispatchEventImpl(item->extension_id(),
-                                expected_event_name,
-                                _,
-                                &profile,
-                                "",
-                                GURL()))
+              DispatchEventToExtension(item->extension_id(),
+                                       expected_event_name,
+                                       _,
+                                       &profile,
+                                       GURL()))
       .Times(1)
       .WillOnce(SaveArg<2>(&event_args));
 
diff --git a/chrome/browser/extensions/extension_process_manager.cc b/chrome/browser/extensions/extension_process_manager.cc
index f64624c..8069686 100644
--- a/chrome/browser/extensions/extension_process_manager.cc
+++ b/chrome/browser/extensions/extension_process_manager.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/command_line.h"
 #include "chrome/browser/extensions/extension_process_manager.h"
 
 #include "chrome/browser/ui/browser_window.h"
@@ -14,6 +15,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/url_constants.h"
 #include "content/browser/site_instance.h"
@@ -55,18 +57,20 @@ class IncognitoExtensionProcessManager : public ExtensionProcessManager {
   ExtensionProcessManager* original_manager_;
 };
 
-static void CreateBackgroundHost(
+static void CreateBackgroundHostForExtensionLoad(
     ExtensionProcessManager* manager, const Extension* extension) {
-  // Start the process for the master page, if it exists.
-  if (extension->background_url().is_valid())
+  // Start the process for the master page, if it exists and we're not lazy.
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableLazyBackgroundPages) &&
+      extension->background_url().is_valid())
     manager->CreateBackgroundHost(extension, extension->background_url());
 }
 
-static void CreateBackgroundHosts(
+static void CreateBackgroundHostsForProfileStartup(
     ExtensionProcessManager* manager, const ExtensionList* extensions) {
   for (ExtensionList::const_iterator extension = extensions->begin();
        extension != extensions->end(); ++extension) {
-    CreateBackgroundHost(manager, *extension);
+    CreateBackgroundHostForExtensionLoad(manager, *extension);
   }
 }
 
@@ -288,7 +292,7 @@ void ExtensionProcessManager::Observe(int type,
                                       const NotificationDetails& details) {
   switch (type) {
     case chrome::NOTIFICATION_EXTENSIONS_READY: {
-      CreateBackgroundHosts(this,
+      CreateBackgroundHostsForProfileStartup(this,
           Source<Profile>(source).ptr()->GetExtensionService()->extensions());
       break;
     }
@@ -298,7 +302,7 @@ void ExtensionProcessManager::Observe(int type,
           Source<Profile>(source).ptr()->GetExtensionService();
       if (service->is_ready()) {
         const Extension* extension = Details<const Extension>(details).ptr();
-        ::CreateBackgroundHost(this, extension);
+        ::CreateBackgroundHostForExtensionLoad(this, extension);
       }
       break;
     }
@@ -470,6 +474,9 @@ void IncognitoExtensionProcessManager::Observe(
     const NotificationDetails& details) {
   switch (type) {
     case chrome::NOTIFICATION_BROWSER_WINDOW_READY: {
+      if (CommandLine::ForCurrentProcess()->HasSwitch(
+              switches::kEnableLazyBackgroundPages))
+        break;
       // We want to spawn our background hosts as soon as the user opens an
       // incognito window. Watch for new browsers and create the hosts if
       // it matches our profile.
@@ -482,7 +489,7 @@ void IncognitoExtensionProcessManager::Observe(
             Profile::FromBrowserContext(browsing_instance_->browser_context());
         ExtensionService* service = profile->GetExtensionService();
         if (service && service->is_ready())
-          CreateBackgroundHosts(this, service->extensions());
+          CreateBackgroundHostsForProfileStartup(this, service->extensions());
       }
       break;
     }
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 77a1942..930ca1a 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -472,6 +472,10 @@ const char kEnableIPCFuzzing[]               = "enable-ipc-fuzzing";
 // attempt to use the existing connection.
 const char kEnableIPPooling[]               = "enable-ip-pooling";
 
+// Enables some extension background pages to be loaded when they are
+// needed rather than when the extensions are first loaded.
+const char kEnableLazyBackgroundPages[]     = "enable-lazy-background-pages";
+
 // Enables MAC cookies in the network stack.  These cookies use HMAC to
 // protect session state from passive network attackers.
 // http://tools.ietf.org/html/draft-hammer-oauth-v2-mac-token
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index c484cc2..3c87392 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -137,6 +137,7 @@ extern const char kEnableInlineWebstoreInstall[];
 extern const char kEnableIPv6[];
 extern const char kEnableIPCFuzzing[];
 extern const char kEnableIPPooling[];
+extern const char kEnableLazyBackgroundPages[];
 extern const char kEnableMacCookies[];
 extern const char kEnableMemoryInfo[];
 extern const char kEnableNaCl[];