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

ui/display/chromeos/display_configurator.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/display_configurator.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
@@ skipping 305 matching lines @@
           return false;
         }
 
         size.set_width(std::max<int>(size.width(), mode_info->size().width()));
         size.set_height(size.height() + (size.height() ? kVerticalGap : 0) +
                         mode_info->size().height());
       }
       break;
     }
   }
-
+  DCHECK(new_display_state == MULTIPLE_DISPLAY_STATE_HEADLESS ||
+         !size.IsEmpty());
   *framebuffer_size = size;
   return true;
 }
 
 const DisplayMode*
 DisplayConfigurator::DisplayLayoutManagerImpl::GetUserSelectedMode(
     const DisplaySnapshot& display) const {
   gfx::Size size;
   const DisplayMode* selected_mode = nullptr;
   if (GetStateController() &&
@@ skipping 575 matching lines @@
     MultipleDisplayState new_display_state,
     chromeos::DisplayPowerState new_power_state) {
   VLOG(1) << "OnConfigured: success=" << success << " new_display_state="
           << MultipleDisplayStateToString(new_display_state)
           << " new_power_state=" << DisplayPowerStateToString(new_power_state);
 
   cached_displays_ = displays;
   if (success) {
     current_display_state_ = new_display_state;
     current_power_state_ = new_power_state;
-    framebuffer_size_ = framebuffer_size;
+
+    // |framebuffer_size| is empty in software mirroring mode, headless mode,
+    // or all displays are off.
+    DCHECK(!framebuffer_size.IsEmpty() ||
+           mirroring_controller_->SoftwareMirroringEnabled() ||
+           new_display_state == MULTIPLE_DISPLAY_STATE_HEADLESS ||
+           new_power_state == chromeos::DISPLAY_POWER_ALL_OFF);

[dnicoara, 2015/03/20 18:36:42]

Shouldn't happen when the display power is all off.
DisplayLayoutManagerImpl::GetDisplayLayout will compute the framebuffer size
based on the selected mode, disregarding the requested power state.

[oshima, 2015/03/20 20:30:08]

when suspending display(s), it may skip actual configuration, which leads to
this state. 

[dnicoara, 2015/03/20 20:37:36]

Acknowledged.

+
+    if (!framebuffer_size.IsEmpty())
+      framebuffer_size_ = framebuffer_size;
+
     // If the requested power state hasn't changed then make sure that value
     // gets updated as well since the last requested value may have been
     // dependent on certain conditions (ie: if only the internal monitor was
     // present).
     if (!requested_power_state_change_)
       requested_power_state_ = new_power_state;
   }
 
   configuration_task_.reset();
   NotifyObservers(success, new_display_state);
@@ skipping 56 matching lines @@
     FOR_EACH_OBSERVER(
         Observer, observers_, OnDisplayModeChanged(cached_displays_));
   } else {
     FOR_EACH_OBSERVER(
         Observer, observers_, OnDisplayModeChangeFailed(cached_displays_,
                                                         attempted_state));
   }
 }
 
 }  // namespace ui