Don't post mirror task before compositor is initialized

ash/display/display_manager.cc

 // 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.
 
 #include "ash/display/display_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <string>
@@ skipping 1050 matching lines @@
     gfx::Display* display = FindDisplayForId(display_id);
     display->SetSize(display_info_[display_id].size_in_pixel());
     screen_ash_->NotifyMetricsChanged(
         *display, gfx::DisplayObserver::DISPLAY_METRIC_BOUNDS);
     return true;
   }
   return false;
 }
 
 void DisplayManager::CreateMirrorWindowAsyncIfAny() {
-  // Do not post a task if the software mirroring doesn't exist.
-  if (!HasSoftwareMirroringDisplay())
+  // Do not post a task if the software mirroring doesn't exist, or
+  // during initialization when compositor's init task isn't posted yet.
+  // ash::Shell::Init() will call this after the compositor is initialized.
+  if (!HasSoftwareMirroringDisplay() || !delegate_)
     return;
   base::MessageLoopForUI::current()->PostTask(
       FROM_HERE,
       base::Bind(&DisplayManager::CreateMirrorWindowIfAny,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void DisplayManager::CreateScreenForShutdown() const {
   bool native_is_ash =
       gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_NATIVE) ==
@@ skipping 181 matching lines @@
       new_secondary_origin.Offset(-secondary_bounds.width(), offset);
       break;
   }
   gfx::Insets insets = secondary_display->GetWorkAreaInsets();
   secondary_display->set_bounds(
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 }  // namespace ash