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

5 files changed, 19 insertions, 18 deletions

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);
     }
   }