Prefer ScopedNestableTaskAllower over manual save/restore

Cleanup.  Changes various calls sites to use the
ScopedNestableTaskAllower class to save/restore nestable task
state.

BUG=None
TEST=Existing unit tests
R=jar@chromium.org, scottbyer@chromium.org, sky@chromium.org, akalin@chromium.org, rsleevi@chromium.org, brettw@chromium.org, tony@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9384024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@121914 0039d316-1c4b-4281-b951-d872f2087c98

11 files changed, 43 insertions, 49 deletions

diff --git a/chrome/browser/automation/automation_provider_win.cc b/chrome/browser/automation/automation_provider_win.cc
index bcc8f63..5165cd5 100644
--- a/chrome/browser/automation/automation_provider_win.cc
+++ b/chrome/browser/automation/automation_provider_win.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -149,11 +149,9 @@ void AutomationProvider::WindowSimulateDrag(
           false,
           MessageLoop::QuitClosure());
       MessageLoopForUI* loop = MessageLoopForUI::current();
-      bool did_allow_task_nesting = loop->NestableTasksAllowed();
-      loop->SetNestableTasksAllowed(true);
       views::AcceleratorHandler handler;
+      MessageLoop::ScopedNestableTaskAllower allow(loop);
       loop->RunWithDispatcher(&handler);
-      loop->SetNestableTasksAllowed(did_allow_task_nesting);
     }
     SendMessage(top_level_hwnd, up_message, wparam_flags,
                 MAKELPARAM(end.x, end.y));
diff --git a/chrome/browser/printing/print_job.cc b/chrome/browser/printing/print_job.cc
index b374b685..aa312de 100644
--- a/chrome/browser/printing/print_job.cc
+++ b/chrome/browser/printing/print_job.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -202,11 +202,8 @@ bool PrintJob::FlushJob(int timeout_ms) {
                     MessageLoop::current(), &MessageLoop::Quit);
   }
 
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
+  MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
   MessageLoop::current()->Run();
-  // Restore task state.
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
 
   return true;
 }
diff --git a/chrome/browser/printing/print_view_manager.cc b/chrome/browser/printing/print_view_manager.cc
index 3a5bdd6..32403c2 100644
--- a/chrome/browser/printing/print_view_manager.cc
+++ b/chrome/browser/printing/print_view_manager.cc
@@ -556,11 +556,10 @@ bool PrintViewManager::RunInnerMessageLoop() {
   inside_inner_message_loop_ = true;
 
   // Need to enable recursive task.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
-  MessageLoop::current()->Run();
-  // Restore task state.
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+    MessageLoop::current()->Run();
+  }
 
   bool success = true;
   if (inside_inner_message_loop_) {
diff --git a/chrome/browser/sessions/session_restore.cc b/chrome/browser/sessions/session_restore.cc
index fb83dcb..7c576dc 100644
--- a/chrome/browser/sessions/session_restore.cc
+++ b/chrome/browser/sessions/session_restore.cc
@@ -475,10 +475,10 @@ class SessionRestoreImpl : public content::NotificationObserver {
         base::Bind(&SessionRestoreImpl::OnGotSession, base::Unretained(this)));
 
     if (synchronous_) {
-      bool old_state = MessageLoop::current()->NestableTasksAllowed();
-      MessageLoop::current()->SetNestableTasksAllowed(true);
-      MessageLoop::current()->Run();
-      MessageLoop::current()->SetNestableTasksAllowed(old_state);
+      {
+        MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+        MessageLoop::current()->Run();
+      }
       Browser* browser = ProcessSessionWindows(&windows_);
       delete this;
       return browser;
diff --git a/chrome/browser/sync/profile_sync_service_harness.cc b/chrome/browser/sync/profile_sync_service_harness.cc
index 34b6124..13fcc71 100644
--- a/chrome/browser/sync/profile_sync_service_harness.cc
+++ b/chrome/browser/sync/profile_sync_service_harness.cc
@@ -746,16 +746,17 @@ bool ProfileSyncServiceHarness::AwaitStatusChangeWithTimeout(
   }
   scoped_refptr<StateChangeTimeoutEvent> timeout_signal(
       new StateChangeTimeoutEvent(this, reason));
-  MessageLoop* loop = MessageLoop::current();
-  bool did_allow_nestable_tasks = loop->NestableTasksAllowed();
-  loop->SetNestableTasksAllowed(true);
-  loop->PostDelayedTask(
-      FROM_HERE,
-      base::Bind(&StateChangeTimeoutEvent::Callback,
-                 timeout_signal.get()),
-      base::TimeDelta::FromMilliseconds(timeout_milliseconds));
-  loop->Run();
-  loop->SetNestableTasksAllowed(did_allow_nestable_tasks);
+  {
+    MessageLoop* loop = MessageLoop::current();
+    MessageLoop::ScopedNestableTaskAllower allow(loop);
+    loop->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&StateChangeTimeoutEvent::Callback,
+                   timeout_signal.get()),
+        base::TimeDelta::FromMilliseconds(timeout_milliseconds));
+    loop->Run();
+  }
+
   if (timeout_signal->Abort()) {
     DVLOG(1) << GetClientInfoString("AwaitStatusChangeWithTimeout succeeded");
     return true;
diff --git a/chrome/browser/ui/views/simple_message_box_views.cc b/chrome/browser/ui/views/simple_message_box_views.cc
index c644a4e..596b7d9 100644
--- a/chrome/browser/ui/views/simple_message_box_views.cc
+++ b/chrome/browser/ui/views/simple_message_box_views.cc
@@ -63,10 +63,10 @@ bool SimpleMessageBoxViews::ShowYesNoBox(gfx::NativeWindow parent_window,
   aura::client::GetDispatcherClient()->RunWithDispatcher(dialog,
       parent_window, true);
 #else
-  bool old_state = MessageLoopForUI::current()->NestableTasksAllowed();
-  MessageLoopForUI::current()->SetNestableTasksAllowed(true);
-  MessageLoopForUI::current()->RunWithDispatcher(dialog);
-  MessageLoopForUI::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoopForUI::current());
+    MessageLoopForUI::current()->RunWithDispatcher(dialog);
+  }
 #endif
 
   g_browser_process->ReleaseModule();
diff --git a/chrome/browser/ui/views/tab_contents/native_tab_contents_view_aura.cc b/chrome/browser/ui/views/tab_contents/native_tab_contents_view_aura.cc
index 795b967..ab1a843 100644
--- a/chrome/browser/ui/views/tab_contents/native_tab_contents_view_aura.cc
+++ b/chrome/browser/ui/views/tab_contents/native_tab_contents_view_aura.cc
@@ -211,11 +211,12 @@ void NativeTabContentsViewAura::StartDragging(const WebDropData& drop_data,
 
   // We need to enable recursive tasks on the message loop so we can get
   // updates while in the system DoDragDrop loop.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
-  int result_op = aura::client::GetDragDropClient()->StartDragAndDrop(
-      data, ConvertFromWeb(ops));
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
+  int result_op = 0;
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+    result_op = aura::client::GetDragDropClient()->StartDragAndDrop(
+        data, ConvertFromWeb(ops));
+  }
 
   EndDrag(ConvertToWeb(result_op));
   GetWebContents()->GetRenderViewHost()->DragSourceSystemDragEnded();
diff --git a/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc b/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
index 2c289cb..58955a2 100644
--- a/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
+++ b/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
@@ -312,12 +312,14 @@ void TabContentsDragWin::DoDragging(const WebDropData& drop_data,
 
   // We need to enable recursive tasks on the message loop so we can get
   // updates while in the system DoDragDrop loop.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
   DWORD effect;
-  DoDragDrop(ui::OSExchangeDataProviderWin::GetIDataObject(data), drag_source_,
-             web_drag_utils_win::WebDragOpMaskToWinDragOpMask(ops), &effect);
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+    DoDragDrop(ui::OSExchangeDataProviderWin::GetIDataObject(data),
+               drag_source_,
+               web_drag_utils_win::WebDragOpMaskToWinDragOpMask(ops),
+               &effect);
+  }
 
   // This works because WebDragSource::OnDragSourceDrop uses PostTask to
   // dispatch the actual event.
diff --git a/chrome/browser/ui/views/tab_contents/tab_contents_view_views.cc b/chrome/browser/ui/views/tab_contents/tab_contents_view_views.cc
index 4325e40..45dde04 100644
--- a/chrome/browser/ui/views/tab_contents/tab_contents_view_views.cc
+++ b/chrome/browser/ui/views/tab_contents/tab_contents_view_views.cc
@@ -362,10 +362,8 @@ void TabContentsViewViews::ShowContextMenu(
 
   // Enable recursive tasks on the message loop so we can get updates while
   // the context menu is being displayed.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
+  MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
   context_menu_->RunMenuAt(screen_point.x(), screen_point.y());
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
 }
 
 void TabContentsViewViews::ShowPopupMenu(const gfx::Rect& bounds,
diff --git a/chrome/browser/ui/webui/downloads_dom_handler.cc b/chrome/browser/ui/webui/downloads_dom_handler.cc
index 92ae005..7fbe6ac 100644
--- a/chrome/browser/ui/webui/downloads_dom_handler.cc
+++ b/chrome/browser/ui/webui/downloads_dom_handler.cc
@@ -268,7 +268,7 @@ void DownloadsDOMHandler::HandleDrag(const ListValue* args) {
     gfx::NativeView view = web_ui()->GetWebContents()->GetNativeView();
     {
       // Enable nested tasks during DnD, while |DragDownload()| blocks.
-      MessageLoop::ScopedNestableTaskAllower allower(MessageLoop::current());
+      MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
       download_util::DragDownload(file, icon, view);
     }
   }
diff --git a/chrome/test/base/ui_test_utils.cc b/chrome/test/base/ui_test_utils.cc
index dc68764..6a580d7 100644
--- a/chrome/test/base/ui_test_utils.cc
+++ b/chrome/test/base/ui_test_utils.cc
@@ -266,8 +266,7 @@ void RunMessageLoop() {
   MessageLoopForUI* ui_loop =
       content::BrowserThread::CurrentlyOn(content::BrowserThread::UI) ?
           MessageLoopForUI::current() : NULL;
-  bool did_allow_task_nesting = loop->NestableTasksAllowed();
-  loop->SetNestableTasksAllowed(true);
+  MessageLoop::ScopedNestableTaskAllower allow(loop);
   if (ui_loop) {
 #if defined(USE_AURA)
     aura::RootWindow::GetInstance()->Run();
@@ -282,7 +281,6 @@ void RunMessageLoop() {
   } else {
     loop->Run();
   }
-  loop->SetNestableTasksAllowed(did_allow_task_nesting);
 }
 
 void RunAllPendingInMessageLoop() {