Don't update framebuffer_size to 0x0 when the framebuffer size didn't change.

ui/display/chromeos/update_display_configuration_task.cc

 // Copyright 2014 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 "ui/display/chromeos/update_display_configuration_task.h"
 
 #include "ui/display/chromeos/configure_displays_task.h"
 #include "ui/display/chromeos/display_util.h"
 #include "ui/display/types/display_snapshot.h"
 #include "ui/display/types/native_display_delegate.h"
@@ skipping 68 matching lines @@
 void UpdateDisplayConfigurationTask::EnterState(
     const ConfigureDisplaysTask::ResponseCallback& callback) {
   VLOG(2) << "EnterState";
   std::vector<DisplayConfigureRequest> requests;
   if (!layout_manager_->GetDisplayLayout(cached_displays_, new_display_state_,
                                          new_power_state_, &requests,
                                          &framebuffer_size_)) {
     callback.Run(ConfigureDisplaysTask::ERROR);
     return;
   }
-
   if (!requests.empty()) {
+    DCHECK(!framebuffer_size_.IsEmpty());
     delegate_->CreateFrameBuffer(framebuffer_size_);
     configure_task_.reset(
         new ConfigureDisplaysTask(delegate_, requests, callback));
     configure_task_->Run();
   } else {
     VLOG(2) << "No displays";
     callback.Run(ConfigureDisplaysTask::SUCCESS);
   }
 }
 
@@ skipping 100 matching lines @@
         return layout_manager_->GetStateController()->GetStateForDisplayIds(
             display_ids);
       }
       NOTREACHED();
     }
   }
   return MULTIPLE_DISPLAY_STATE_INVALID;
 }
 
 }  // namespace ui